View Full Version : Lift Kit for Duramax
I've been having fun with my new 2004 Duramax and I love it. :D Except for the clearance! :( Spoiled by my 89 Toyota SR5. So I'm looking for a bit of lift.
There seems to be lots of 6" lift kits out there but is there any 2-3" lifts that can be put on the Duramax? I intend to put on 255x85R16 tires to raise the axle/diff clearance by an 1 1/2" and raise the suspension another 2-3" with a lift kit. I can't go more that 5" max over stock and still park in my garage.
Any recommendations?
I don't think you will find a 2-3" suspension lift. A lot of guys that simply want to raise the front end 1-2" to level the truck out crank their torsion bars but there are potential issues with that regarding wear on front-end components. Still, it seems to be a very popular route.
I have the Rancho 4" lift kit on my 03 and love it. 6" is the most popular from what I found also ... with RCD being the most popular.
My requirements were also to be able to park in my garage so I did a lot of measuring, etc. to make sure I would still fit after the lift and new tires/wheels.
Note however the lift kits aren't cheap but IMO are the best option of raising an IFS truck. I went with the Bilstein 5100 SS shocks and my truck rides like a car ...actually improved my ride considerably and I had already installed Bilsteins before the lift.
I went with a 315/70R17 tire/wheel combo and combined with the lift I got just over 6" total height increase and I do still fit in the garage (barely).
Thanks Tophog.
One place I contacted suggested that I could do this on the cheap by installing riser blocks at the rear and torquing the front but I also had reservations about this...however the price ($500 Can) is very tempting.
I'm leaning towards taking your advice and going with the Rancho 4" lift even though its 10x the price ($4300 CAN). I suspect I'll be much happier in the long run if I do this right.
I have a canopy on my truck, my greatest height can't exceed 81 1/2". What was your finished height with an empty truck and your new tires?
Many thanks for your time and help tophog...
Anyone else have any suggestions???
You can't really use riser blocks on the rear and crank the torsion bars ... unless you want the factory look with the sloped front end. You can't get much height by cranking the torsion bars before the bolts bottom out ... I tried this on my truck before getting the lift and I think I only got 1.5" before the DS torsion bar bolt bottomed out.
I will do some measuring and post the numbers later on.
VFRRider
01-07-2004, 16:07
I have H2's, and with the TBar crank, I'm up about 4 - 4.5" from stock, most of that is ground clearance from the taller tires. Had to adjust my garage door, but my truck still fits inside.
Mike
I have twice looked into this. The best option is a lift kit. I like the Rancho lift. They say 4", but you do have another 1.5 - 2" if you rasie the torsion bars. The only downside to the Rancho--in my mind--is it increases the front track width, making the front track width wider than the rear. I suppose it's very hard to tell just by looking at it and I don't suppose it casuses any problems, but it***ut doesn't seem right to me.
All the other kits are 6" lifts. Some are true 6" lifts allowing a up 7.5" of total lift. I think the Superlift will allow you to lower the nose to 5", but if you do so you put the front diff lower to the ground.
Right now, I have the Hill 4WD Levelling Kit. they are specially designed torsion bar keys that allow up to 3" of lift. They caution that anyting over 2" can make the truck ride rough, but with the diesel engine, they say 2.5" usually isn't a problem. With my Frontier front replacement adding more weight to the front, I have had my bars as much as the full 3" without a bad ride. However, I currently have them at 2.5" and the ride is very good. I am going to install some 1" rear spacers, to keep about 1.5" of nose down in anticipation of trailering. After I roll back the inside of the innder fender well, I'll probably drop the nose back to 2".
Folks that trailer with the nose lifted too much say the ride get's choppy. This could be just a tongue weight issue, but I think if you plan to tow you ought to have close to the 3" nose down rake GM put in our rigs. But that is just my guess right now.
I initially rasied the nose because while hunting last year, I filled the skid plated full of mud and grass. After rasing the nose 1.75", that was no longer a problem.
Based on the research I have done into the HDs, we have very stout CV axles and rasing the torsion bars within the factory droop limits doesn't seem to have a negative effect. There are many rigs out there with 60-100K on a raised nose. The problems with CV axles with raised torsion bars seem mainly to be a Toyota IFS and the 88-98 GM IFS problem.
Remember that when you jack the nose up and down, you need to reset toe. As you raise the nose, toe-in increase, as you lower the nose, the tires toe out.
The levelling kit cost $150, an 8" gear puller from Sears was $30, and the 1" blocks are $50. Call these folks and talk to them. They sell the levelling kit as well as other lift kits, and seem to have a lot of experience with GM IFS.
http://www.hill4wheeldrive.com/
Blaine
The Hill 4WD Leveling kit is simply a different set of factory GM torsion bar keys. If you go to FullSizeChevy.COM, there's a thread (sticky, always at the top) about this under their offroad forum. You can get the same effect by simply twisting up your torsion arms right now - the leveling kit simply moves the range of adjustment, that's all.
The truck can ride rough at 3" total lift...because you're then (basically) out of travel in the front shocks. Not a good thing. An extra twist or so on the torsion bar does nothing to change its spring rate, just the preload.
I was ready to do this ~2" lift but in decided against it. I'd only be doing this to run 285's and (I'm told) I'd still have to trim the front end for proper fitment, and that would interfere with the winter bumper front. If I get a new bumper, I may reconsider this mild lift.
Another concern is it raises the front suspension off the front bump stops which are intended to be part of the suspension - effectively decreasing your front spring rate because you'll only be using the torsion bars for the springs. If you drop those bump stops the appropriate amount (to match how much you've twisted up the torsion bars), then all should be good and correct.
There are also a few trucks reporting inexplicable vibrations. A lifted truck will do that, but I'm not sure why this mild bit would - it really shouldn't. Still, people have reported this, and my truck only sees highways miles.
I, too, spent a lot of time investigating the kits. There are basically two kinds of kits, those with new knuckles and those that drop the whole front end. I'm not keen on the knuckle lift (like the Rancho, basically a copy of FabTech's) for a variety of reasons including the change in the front track width, increased angles on the CV's, etc. I prefer dropping the entire front end because that will keep your geometries (CV, etc.) and spring rates correct. Of this bunch, I would pick the Pro Comp 6" over the Superlift, because even they are very similar, the Pro Comp steering fix is a bit better.
In the end, I decided against a 6" lift too because our trucks have notoriously weak steering components and because I use the truck as a truck, and raising the truck a total of 6" in suspension and 2 inches in tires would make it that much harder to hoist things in and out of the back of it. I've got my toy 4x4 so this one can stay stock.
--Rob
Thanks a lot AFP and Ryeguy. This Hill 4 WD system sounds like a better alternative to just cranking the existing torsion bars. I'd be real happy with just a 1 1/2" front lift. I intend to put 2" riser blocks on the rear as well to maintain a nose rake with my canopy and KargoMaster roof racks on the back. The combo of the two should work well.
I discussed this with someone who knows a bit more than I do about this stuff and his concern was that with so much of a change that I might not be able to get a proper wheel alignment afterwards.
I take it that your experiences are contrary to that and you've had no problems with alignment and parts wearing out prematurely due to unusual angles or stress?
Anyone else use the Hill System??
Rob,
My research and experience with the Hill Keys is just about the opposite of what you are describing. No flames or ill will here, just a different take. It is an interesting discussion.
The Hill Kit is not really just another set of GM keys. GM keys do not always have the amount of travel the Hill keys do and can run out of travel befoe 3" is reached. The Hill keys ride well at 2.5" on my truck and okay at 3". I have heard all kind of ride complaints about the "green" keys and other factory type keys. I'm not sure why this is, but my Hills have ridden well for over a year now.
The rough ride on some trucks at 3" of torsion lift is not due to the shocks being out of travel. The total front suspension movement is the same with lifted torsion bars, it just resets where "zero" travel on the shocks are. My shocks--Bilsteins designed for a stock height truck--only come close to their droop limits if I raise the nose with a jack and let the suspension go to full droop. Regardless of how I set the torsion bars, full suspension droop is the same.
Also, there is no additional pre-load on the torsion bars. This has been coverend in depth in other posts here. All you do is re-index the torsion bars when you raise them with the keys.
The choppier ride is because anytime you raise the nose you shift the CG aft, transferring more weight to the rear. This reduces weight on the nose of the truck. The same thing happens when you tow a trailer, and that's why guys sometimes report a choppy ride while towing.
I personally haven't ever heard that the front suspension is supposed to ride on the bump stops. The purpose of bump stops is usually to limit suspension travel. I am not 100% sure here, but it does not make sense that torsion bars were designed to be aided by a rubber or even poly bump stop. There is little compression to the bump stops and repeatedly hitting them would make for a very jarring, rough ride. If anything, the closeness of the A-arms to the bump stops indicates how concerned GM is with not letting the nose droop too much. However, i would be interested to hear from a suspension expert on this.
I am not sure the Rancho folks would agree that their kit is a copy of the Fab tech. Rancho has been around a long time. I've been told the Rancho is the sturdiest of the kits because of how they brace it. I am not bothered by drooping the CV axles, actually I prefer it because it raises the front diff higher off the ground and does not hurt out HD CV axles. However, my ultimate choice in a lift kit would be a 4" Pro Comp or Superlift with Bilstein shocks.
I have been told by an independent suspension shop the 4" Rancho's spindles provide the same drop as the other brand's 6" kits. I guess that all gets into "true lift"--factoy torsion bar setting yields the quoted lift figure and the other--requires raising torsion bars to get the advertised lift. However, it seems everyboy's 6" lift is a true lift...............
Blaine
[ 01-08-2004, 07:23 PM: Message edited by: afp ]
AFP and TH,
the "bump stops" as you call them on the full size trucks are in fact called auxiliary springs.
they were designed to carry some of the load of the front end they are not a positive stop like jounce bumpers (bump stops) would be.
i have also been studying about some lifts. i don't particularly like knucle drops because the front end travel limits are greatly reduced by the cv joints binding. i would rather buy one that needs a new front drive shaft because the front articulation limits are maintained.
GM also has a different "key" than the green one that lifts the front further than the green ones.
the part number for that one is 15592574 and should have a white paint dot on it.
i have been running bfg 285 mud's on the stock rims on my truck for almost 65,000 miles and have had no trouble with them really hitting anywhere except for the front left inner wheel liner. a heat gun should take care of the hitting but people should be very careful because the gun gets VERY hot. i have so far had no trouble my cv joints or other steering components.
just thought you guy's should know.
jobbie
Thanks a lot for the info Jobbie. I take it then that you recommend moving the bump stops as well since they act as auxillary springs.
Jobbie: thanks for the other key number. A question on your truck: any interference between the 285's and a winter front the clips all around the front bumper and air dam? That heat gun is an interesting idea. I'm also running the factory mud flaps, that the 265's rub on at full lock. And how much is your front end raised?
AFP: good discussion:
The Rancho and the FabTech both use a similar approach in cutting off the mount that's on top of the center section, then bolting on a cradle with a built in skid plate. They also use the same recast knuckles (there'll only one shop casting these babies). The Fabtech kit came out before the Rancho. Whether Rancho uses the same brackets EXACTLY or not, it's not a big deal, it uses the same basic approach to lifting the truck and the design of the brackets. The RCD kit is similar too but the bracketry is different.
Given what the keys do - simply re-index the torsion bars (you're technically absolutely correct there, I just think of it as changing the preload but it's the same thing because your torsion bar spring rate is constant), it really shouldn't matter whose or what keys you are using given a particular ride height - the ride quality will be defined by the torsion bars and (hopefully) the jounce bumpers/bump stops. The keys are stationary during normal suspension movement. The jounce bumnpers will give you a variable spring rate where the torsion bars won't - unless they change in diameter.
Now, the more you crank up the torsion bars (or re-index) the less effective droop you have because you haven't changed your range suspension movement. If you lift your truck 3 inches, you'll have 3 inches more up wheel travel, but 3 inches less down wheel travel. As you limit your wheel droop, you will see effects to your ride quality.
I really don't think the change of weight distribution on our trucks (6700lbs unloaded, heavy suspension) from raising the front a couple inches will noticably affect your ride quality. Choppy rides when loaded are more likely attributed to using the rear overload springs.
--Rob
Ryeguy and Jobbie,
This is a good thread! What I thought I had mostly figured out I realize I only had partially figured out.
I spoke to the Hill 4WD drive guys. Along with their torsion bar keys, they sell and install Rancho, RCD, and Tuff Country lift kits as well as other suspension stuff. They have't done a Pro Comp yet. They have worked extensively on HD suspensions. I also spoke to FWPW the mail order guys. I'm not sure the info is as good from FWPW.
First to the ride issue with cranked torsion bars. The Hill guy confirmed that the choppy ride comes from shock travel issues. He said his company has contatced the three major shock makers to try and get them to make an intermediate lift shock. Actually, all that is needed is a stock travel shock with a 2-3" longer shaft. He said the shock companies make either stock height shocks or shocks for 4" lifts and more.
He explained when you raise the nose with the torsion bars, you put the shock lower in it's dampening area where it's less effective, like Ryeguy said earlier. This is the main reason for the choppier ride. I guess the weight transfer issue isn't as big as I thought it was.
Now my truck rides stock like at 2", very good at 2.5", and okay at 3". This is very likely because of how I installed my Bilsteins. My goal was just to make sure I didn't bottom out the shocks before hitting the bump-stop springs, but it looks like I got more than that.
I was able to get a 1" spacer under the top shock mount, which put the shock 1" closer to it's center of travel and keeps it in it's range of good dampening longer. Now that the rubber shock mounts have been on for a while they are likely compressed--I'll bet I can get another 1" spacer under the top mount. I'll have to check to make sure the shock doesn't top out if I do this.
The Hill guy said the bump-stops were indeed springs of a sort (Ryeguy you are right again), but they didn't really do anything well other than function as bump stops. I guess sort of a progressive or gentle bump stop. If I get another spacer under the top mount of my shocks, then I could lower these bump-stop springs to limit downward travel if needed.
The Hill guy also said there is a lot of suspension travel with th HDs. He said they have removed the shocks to see what they could get and it was well above 3". Even with the shocks completely removed and the suspension resting on the bump stops, he said the CV joints were not close to binding.
I have tried to visualize while the Hill keys might be better than stock keys. I makes sense to me as well that a simple re-indexing of the torsion bars should yeild the same results with whatever key you used. The Hill guys say their keys have more adjustment than stock keys, and it is not good to have the keys binding against the frame.
Okay, this is easy to see. After installing the Hill keys I can easliy see how they get more adjustment out of them. However, I can't see how their design affects ride quality either, but that's what I thought I heard them say. Maybe I heard wrong.
My good ride with the Hill keys may be due to my special mounting of the shocks and the fact that I'm using Bilsteins. Perhaps guys that have had a bad ride with cranked green keys were using stock shocks--which aren't all thet great anyway, and maybe worn out--and the added lift moved the shocks way out of their ideal dampening range.
Lift Kits..............
Both the Hill guy and the FWPW guy said Pro Comp is the only HD lift Kit that doesn't increase wheel track. They both said the Ranch will move the front wheels out 1-1.5" more than the rear wheels. The Hill guy said the advantage to the Spindle drops (everybody but Pro Comp) is strength, ease of install, and ease of returning to a stock lift.
He said the Pro Comp used a lot of brackets and hardware to lower the front diff, and all that made for a less strudy installation. I guess that is why Hill prefers the spindle drop style. Of course, the FWPW guy says the Rancho is good but the Pro Comp is the next best thing to sliced bread.
I asked the Hill guy about using spacers to extend rear wheel track to match the increased front track caused by the spindle lifts. He said the HD rear end is arguably the strongest rear-end of any light truck and is very stout. He said he's torn down a HD rear--I forget what they were doing to it. For 60,000 miles, this rear had been wearing 44" tires on 14" wide rims. He said there was virtually no wear on the unit anywhere. He said those 14" wide rims would have put at least as much stress on the axle bearing as I would with 1.5" spacers and 285s on 8" wide wheels. He said there is a company that makes very nice billet aluminum spacers from a special alloy that would work well for my application. he said they are spendy becasue of the special alloy used.
I guess I look on the Hill guys info favorably, because he knew I had only bought $200 worth of stuff from them and that if I did get a lift kit it wouldn't be from them due to my location. He had no motivation to try and sell me anything, unlike the FWPW guy. All the Hill guys I have talked too really seem to know their stuff.
Don't know how much of this is 100% correct, but it does give us some more stuff to ponder.
Blaine
AFP and Ryeguy...what would be involved in lowering the bump stops? I've ordered GM White Keys (supposedly have greater travel than the Green keys) and intend to have a shop install them etc. as well as the 2 1/2" riser blocks in the rear next Fri.
Also...re the shocks for the rear...I take it that the riser blocks will also affect travel on the rear shocks and that the 2 1/2" change will be hard to accommodate if shocks are only being made to accommodate 4" and more lift kits (as per afg).
So...would having a new mount welded up 2" higher up on the existing rearend bottom shock mount bracket (rather than the axle itself) solve that problem. In other words...all that would be done is the bottom mount of the rear shocks would be moved up the bracket by 2". I could use stock size shocks in the rear. Nice thing is if that works (after a suitable trial period), then I could have the rest of the original shock mount bracket cut off (the part that dangles below the bottom of the rear axle) to give me more overall ground clearance and less opportunity for hangup on rocks etc.
Remember guys...I'm mechanically challenged ...be gentle if I've suggested something that is totally stupid.
Thanks...
TH,
Realize I'm throwing out hunches on a lot of this.
Looking at the bump stops, it appears there are limits to how much they can be lowered, maybe 1/2" or so with the factory threaded shaft. I'd have to fiddle with them to see if there is an easy way to get them lower.
Before installing higher shock mounts, you need to first see if they will work with the lift block as is. Next, the Hill guy was referring to front shocks, maybe there are rear shocks that are 2-3" longer than stock.
Blaine
Ok, guys
My wife was hanging on me to get off this site and go plug a hole. Here's the truth, Fabtech, lifts your truck, as they did mine, but the front tracking is 5 1/2"s wider than the rear. This may not seem to be a prob to you guys, but I have a crew cab and it chews the hell out of my paint and back windows! I just talked to a body man, he said it would take about $2000 to make the Bushwacker cutouts work. Why? because you have to cut the front wheel well, then you have a hole and need to cover it. If you are NEVER gonna go back to stock, go with the Pro-Comp lift! If you go with the Fabtech, be carefull, I put $5000 into my truck, and I still need another $2000 to make it look nice
AT-
guy's,
i hate to tell you this but my truck is a gasser not the actual truck i would like! i just got married and SHE won't let me get a new one as of yet. :(
anyway i have no real interference in the front unless my shocks start to give out. which happened 2 summers ago. my tires will rub at the back drivers side on a left turn hard lock and going over a bump. other than that i have no problems. i have turned the torsion bars up around 2 to 3 turns though. all of this was before my 3" body lift. before you all complain about body lifts check between your cab and frame to see if you have one from the factory. ;)
by lifting up the front suspension and NOT changing your shock to accommodate the new ride travel you can have a shock explode on you. :eek:
i have talked to a tenneco engineer here at work about this extensively.
lowering the bump stops should entail having a new spacer made with a thru hole in it so you could put new longer bolts through. do not do this to the shock because the shock could bottom out and do what i mentioned earlier. try to get new ones for the added lift. see when shocks are trying to get close to their designed jounce limit the gas that is in the shock has only so much area that it can fill if you try to push it (shock piston) further up into the tube it has no place else to go except out. then POW! redface.gif
also the knuckle drop will alter your jounce and rebound heights that were set from the GM engineering staff. when you put the spacer into the front axle shaft you push it out that length.
which in turn WILL stop it from moving to full rebound (droop, sag or whatever you want to call it). the cv's will bind! the cv joint doesn't have to bind completely either. there is only so much articulation (angle) built into them and you can't add more with out building new ones.
GM has all of the different "keys" and torsion bars so they can figure out the ride height by computer selecting the ones that will work to give the correct Z height with the options on the truck. by changing the "keys" you should in effect not be changing the ride quality just the height, but, you will need a front end alignment.
i would rather get a real suspension lift that still keeps the correct geometry. but they can be a little more expensive than the knuckle drop because autotracs need a new front drive shaft. :(
dmaxallitech i do log on sometimes. smile.gif
Thanks Jobbie...I followed everything you said right down to the word POW! :D Then you lost me! :confused:
Not certain what you mean by knuckle. What part is that?
Anyways...after its all said and done, are you saying that if I install the other keys (GM White Keys), I will get a front lift of about 2" but that dropping the bumper stops down to where they touch the torsion bars (like when stock) will cause problems with the CV joint (binding)?
Or are you saying that regardless of what I do, torquing the torsion bars to raise things 2" will cause the CV joints to bind regardless of what I do with the bumper stops?
I do use the truck off road (gumbo mud, deep ruts, deactivated roads with dug ditches, snow, soft moss with mud under it) so I will be bouncing around a bit but I'm always careful and take my time...unless I don't see the hole!
I will be going with 255x85R16 or 285x75R16 tires to give me another 1 1/2" in height over stock.
TH,
No doubt Jobbie had a shock explode, but that is a rather rare occurance. The majority of guys who lift the front end of their HDs 1-2" via cranking torsion bars have no problems.
As to the suspension travel........ We are not changing the total amount of suspension travel by cranking the torsion bars. However, we are moving the shock out of it's mid-point when the suspension is at rest, which is less than desirable. My Bilsteins seemed to work very well when I had them about an inch from their midpoint. I do not know how close to the mid-point they have to be for optimum performance, but my experience shows an inch out is not an issue.
The probelm we run into with putting spacers under the top mount when we crank the bars--like I did--is we are effectively limiting the distance the shock can compress. A better solution that compressing the shock would be to move both shock mounting loacations. That would keep the shock at it's mid-point and allow full shock travel in either direction. Simpler yet are longer shocks, but nobody makes them in the intermediate sizes for out Dmax yet.
I am going to experiment some tomorrow. I will try and put another spacer under the top shock mountand see how the truk rides. At it's current setting of 2.5" over stock, the ride isn't as good as stock. At 2", it is the same as stock. If having the shock at it's mid-point is the key to a good ride, then I'll have my stock ride back when I add the additional spacers.
The concern I have is compression travel on the shock. I will probably need to raise my bump stops to limit compression.
After installing the additional spacers--if I can--I'll install my 1" rear blocks. This will show if increasing th forward rake of the ruck and allowing more weight to transfer forward will soften the ride. I am not really concerned about extending the rear shocks and inch, as the Bilsteins show no change in performance when an inch out.
Blaine
TH and AFP,
TH i am looking at those "keys" also. GMparts direct (http://www.gmpartsdirect.com/results.cfm) is a great place if you have the part number.
when we do a lift like this we should be moving the auxiliary spring with it. these "springs" do carry some load on them and they have a built in variable to them. it is because of the material that is being used in these "springs".
what i am saying about the shocks is that there is an internal piston that rides up and down and it is set with limits as to when the gas is at full compression inside of the shock. when you lift up your truck to get the extra 2" or 3" your shock can make contact inside of the shock body and since the gas that is inside the shock has no place to go to (only on monotube shocks) it will leak. (leak is better than explode) :D
AFP is correct in the fact about limiting the shock travels.
the best thing to do for shocks it to find some that are designed for the new raised height of your truck.
the knuckle of the truck is the big part that the front axle slips through and it is also the part where the upper and lower ball joints are located.
the problem with the cv's binding will NOT be present with just a turn of the torsion bar.
GM has these designed to go the whole range of "keys" and torsion bars that is in their library.
it is when you change to a new knuckle that has effectivey lowered the original point of where the axle comes through it. the longer knuckle as compaired to the stock one. which WILL change the actual lower suspension travel points but not the top ones. which will stay where they were designed to. the lower ones will move around 4" to 6" depending on the lift kit you bought.
these kits with the knuckle drops are fine if you don't do any serious off roading where your suspension hits the full jounce and rebound (droop) points. the cvs will bind because of the spacer that is supplied changes the angles of the axle. it pushes the axle mounting point out from the axle body tword the side of the truck a given length.
i like the ones that move all the brackets down for these facts. the problem like i stated before is the new drive shaft.all of the lifts i have seen of this variety looked like they were well thought out. but you have to pay to play. :D
but i live in michigan where the roads are rotten and have found full rebound many times. :mad:
i too do some off roading but the only problem i find is that these trucks are so darn wide. :D
friends at work think i am nuts because whith in a few months of purchase i was out in the woods driving through raspberry patches and logging roads. sounds normal to me. ;)
TH by the way i haven't had one explode YET. :D
Jobbie,
Nobody makes shocks for HDs yet that are for 2-3" more travel. I am not yet convinced on the utility of the bump-stop springs as helper springs, and neither is the Hill 4WD guy. However, I think using them as bump stops and lowering them to prevent the shocks form bottoming out is a great idea.
Why Oh Why doesn't Pro-Comp offer a 4" kit. This would solve all our concerns..............
Blaine
TH,
i should tell you now where i work at.
i work for GM in warren at the tech center. i used to work in pontiac at the truck design center but had to relocate to warren. :(
i do know a little about front and rear suspensions. ;) i talk to the people that have designed these and all other light duty suv's.
if you want to talk personally here is my email account.
ihateibms@yahoo.com
i too would like a 4" rather than a 6" lift.
but that is just because i am short. :D
I installed the 1" lift blocks in the rear. I used the factory u-bolts, but I had to remove the washers. I have about 1 thread extedning out form each nut. I also "loctited" the nuts on. Although this is very secure, I'd rather have slightly longer u-bolts. The rear lift didn't seem to make a huge difference in the ride of my truck, so perhaps the weight transer isn't an issue.
I decided against installing another spacer under the front shocks for now. I really didn't want to limit their compression travel anymore. However, I did bring the nose back down 1/2". This was two turns of the torsion bars. I get around 1/4" a turn. This made the ride stock. Probably better than stock since I'm running Bilsteins. That last 1/2 inch seesm to really make a big difference.
Anyway, my truck is now lifted 1" in the rear and 2" in the front. I think this is about all I can get with a good ride and good component longevity. BTW, lowering the nose 1/2" toed the front tires out about 3/16 of an inch. It also widened the track by about 1/4".
I'll probaby lower the bump stops a bit. Right now, the shock bottoms out the same time the suspensions bottoms out, and I'd like the shock to not completely bottom out. You know, for those times I'm jumping with my truck and the front suspension is fully extended......
I will have to roll back the inside corner of the aft portion of the fender wells. Right now I have almost an inch of clearance when the steering wheel is turned about 3/4 travel. That really isn't enough--a hard bump during a hard turn can casue a rub, and I'd be very limited with chains. However, rolling back just the inside aft portion of the sheet metal on the fender will easily give me another 1-1.5" of clearance with my 285s an 8" rims.
Blaine
afp...what size, model of Bilstein shock are you using?
Thanks again for all your advice on this...I'm certainly getting my money's worth out of this site!
Same goes to everyone else who has taken the time to reply...much appreciate. :D
I am not sure of the exact model. They are just the Bilsteins for HDs. I got them form John Kennedy, and the cost about $65 each. Here is his website:
http://www.kennedydiesel.com/
Good thread!
Superlift is another manufacturer where the whole front end is dropped with brackets. There are some subtle differences between it and Pro Comp's. For example, Pro Comp uses heims and Superlift uses poly bushings in the drop brackets for the steering - and for that application I'd prefer heims. Pro Comp also includes the front end braces to another crossmember, where Superlift's is an option. I don't work for Pro Comp, but I think their kit for our trucks is a good one. The brackets are all sturdy, lots of bolts are used, and it seems well designed. It would be my choice. BUT shops don't like this kit because it takes a LOT longer to install correctly - to make sure all the brackets are located correctly, aligned, etc. More chance of error if you're running against the clock to make $ on the deal.
Superlift claims theirs is the only kit where the vehicle can return to stock after installation. I disagree on 2 counts: Pro Comp would require the same amount of work, and both of these kits require welding on installation, so either take the truck back to 100% stock. The other kits with the drop brackets seem to require a LOT of mod's that won't be reversable. This includes Rancho and FabTech - you'd need a new center section to take it back to stock because you've cut a mount off it during installation of the lift.
Shock length vs: compression for correct jounce control: not an issue for some kinds of shocks. There is a concern about over-extending or compressing shocks - particularly at speed. It's not an issue regarding no place for the gas to go, but instead the piston bottoming against the inside of the body. We haven't had any issues when rock crawling, but I wouldn't want to bottom out a shock at highway speed. Depending on what you do with your truck, I wouldn't be against running a slightly longer than ideal shock in the rears of our trucks - if you don't haul a load, then you aren't going to fully compress the rear springs to compress the shocks when offroading - particularly when they are inboarded - less leverage. No prob's relocating the rear axle shocks mounts up a bit too - if you run a longer shocks you'll likely get more travel, but you're only talking a little bit because it's such a heavily sprung truck.
When cranking up the torsion bars, I'm not as concerned about front CV's binding as I am about the extra wear. If you're offroading, that's not a big deal because you'll see faster wear from use anyway. My DMax is only on the street, so a mild lift would only be for looks, and then it becomes a looks-vs.-wear decision. Also, the more you crank up your arms to change your static ride height, the more the tire moves in and out from under the vehicle during suspension travel due to the change in the static A-arm locations - result: more bump steer.
Aluminum spacers to widen the rear track: get some steel ones made up. We've seen aluminum distort when offroading. It's a bit more weight but no biggy. If memory serves, the dually rear end simply uses spacers anyway, but those may be too deep to match the change in the front track width for spindle-lifted trucks.
Lowering the front spring jouncers: actually a half-inch is likely all that's needed. 2.5 inches at the wheel is likely about 0.5 at the bump stop/spring.
Body lift on a HD: not a good idea if you want to run a 5th wheel hitch. I heard a rumor that you couldn't put a body lift on a DMax anyway, but that seems odd...
Rear lift blocks...will induce more axle wrap. We already have axle wrap with our trucks ('specially if the engine is tuned up). A 1" block isn't a big issue, but I wouldn't let the truck hop for long - that's what breaks parts - diff's and U-joints and...
Amount of lift: I'm not sure why the spindle lifts are all around 5-6 inches lift. They should be okay with less, but it may mean another spindle casting. I'm not keen on the CV spacers either, just seems like a hokey design. For the lifts that drop the whole front end geometry down (thus sometimes necessitating a new front driveshaft), it's a lot of work for installation, and cost vs. work vs. amount of lift gained will determine "how many of these will we sell", which means they think poeple who are going to this effort will want at least 6 inches. Plus, drop brackets just take up a certain amount of room, too. For people with less lofty goals, just crank up the torsion bars and make it work.
--Rob
guy's
you are all going to love this one i just heard from work this morning.
anyone changing the front "keys" will void their warranty! i heard that straignt from the lead engineer for the GMT800 (full size pick ups).
he said that GM tried to get more lift by changing the "keys" and that they were tearing off shock towers and over extending the upper ball joint until it came out of the control arm.
the upper arms are not serviceable. he said the ball joint failure was from changing the shock to a longer one to compensate for the new rebound height and the tower breaking off or tearing was due to the stock shock being too short at rebound and the lower control arm pulling down. he said there was also more problems like now with the longer shock you get the shock into compression too soon and it will damage it on jounce. on most of these failures they were pushing it right up to the limits.
he also said the most desireable lift was any lift that doesn't use a knuckle change to gain the lift. but this applies more for the guy that is going off road and not just to car shows or street driving and won't be pushing the suspension to it's limits.
now remember real world testing and GM's pushing it to the limit aren't the same thing. i know there are a lot of guy's out there that have changed the "keys" and haven't had any problems and probably won't. just be warned.
Jobbie,
Thanks for that post!
I'm off warrantee, and I haven't heard of anyone wrecking the upper arms during "normal" driving.
Still, it's good to know. I'm curious how hard GM pushes things in their tests too. Still, I think it warrants some discussion:
What limits the suspension droop right now? Sounds like the stock shock (where the Bilstein will give you a bit more droop, right?). Really, I have never, EVER seen a stock shock break a mount due to over-extension - why? - because you've only got unsprung weight pulling it down (with a bit of inertia). I have from over-compression because you've got the weight of the vehicle on it (plus a lot of inertia) (through the shock).
Over-extending only will place the unsprung weight of the vehicle onto the shock mount (via the shock). That's tires, A-arms, rims, hubs. 100's of pouds. You might have some load from the torsion bars being re-indexed too much, but that would be in 100's and 1000's. But the shear on the bolts (and we could calculate for the steel around there as well) will be best measured in 10,000's of pounds - loads you'd see when over-COMPRESSING a shock - not over-EXTENDING a shock.
I have a real tough time believing that the mount will break before the shock tearing apart - those eyes are only generally tack welded to the body of the shock. Surely, the shock mounts are stronger than a couple tack welds on the shock itself!
And, remember, you've only changed the effective droop - no other components. So it isn't a big change from factory when it comes to loads, just when it comes to ride quality.
So, let's change the effective droop by putting on a shock too long. If it completely compresses, then I could see ripping a mount off an arm or frame, but that's not what is said here. And that can be remedied by adjusting the bump stop. I can also see how a ball joint would be over-extended due to too much travel. But, that sounds like GM simply selected a shock that was too long for these tests. Then again, I haven't heard of anybody with a lift kit complaining about blown upper ball joints - and that will have a longer shock allowing for more suspension travel (read droop).
Of course, there are other solutions to all of this (besides fitting a better length shock) - limiting your up wheel travel for the longer shock, limiting straps for droop, but it comes down to at what point is it the owner's responsibility and no longer GM's (for warrantee). We've already crossed that line. My hunch is that the GM engineers are smart enough to go through these scenarios and they're just playing it safe - saying leave the truck alone or it's your responsibility. And can't blame them for that.
Side bar: Doesn't GM have a snow plow package? Does that package use different torsion arms, or different keys, or both, to make sure the truck's Z-height is correct with a snow plow mounted to its nose?
--Rob
Does the Superlift increase the track width? I initially I thought it didn't, but was told otherwise by both the FWPW and Hill 4WD guys. Then again, neither place really pushes Superlift. When I talked to the Superlift rep, he told me they were going to offer Bilstein shocks with their 6" lift HD kit, but I don't remember asking about track width.
My biggest concern with my lifted torsion bars is if there will be added wear on the CV boots. Raising the nose droops the CV axles and it appears to push the rubber boot more in on itself than if the CV axles were horizontal. The Hill 4wd guys say the difference in wear on the CV joints with cranked torsion bars vs stock bars is very minimal.
When I searched for spacers, I did find some steel ones. Like you, I am more drawn to steel, but some of the newer aluminum alloys are extremely durable. The good spacers of either type seem to run $100-$300+ for a pair.
I do not really like the idea of a spacer. However, the Rancho 4" kit is very stout and should only add 1.5" in width to each wheel. If I went with the 6" Pro-Comp kit, I'd need to run 35s on 10" rims, and that would have to extend my front wheel track by about 2" on either side. I currently have 8" rims and there just isn't any room for more offset to the inside of the wheel.
So I guess a Rancho kit with 1.5" spacers for my rear wheels wouls be less wide than the Pro-Comp kit if I ran 10" rims. I would insist on 10" rims with the 35's because I will be trailering with this rig, and I want a stable ride when towing. A 35" tire on an 8" rim would allow the side walls to roll a bit. I know many say you can run a 35" tire with an 8" rim, but after going from 265's on 6.5" stock rims to 285s on 8" rims, I can tell you the difference in stability is significant with rims on the narrower end of the range for a given tire size.
Of course, my truck runs great with the Juice and 285s. Going to 35s would require a gear change--4.10s would make it close. When I add in gears, tires, and wheels to the 6" Pro-Comp lift, it gets expensive. As I realize such a set-up would increase my track width more than the Rancho kit running the wheels and tires I now have, the Rancho--with wheel spacers on the rear, seems better all the time. I just don't know if Rancho has a shock as good as my Bilsteins.
Blaine
rob,
yes GM does have a snow plow prep package. it is a VYU option code.
mine actually has it. most of that is just different torsion bars and a button on the dash for a caution light. there might be some other differences but i haven't looked into it because i don't have a plow.
you also have to realize with the test here is that quite a few of them are on a 4 poster. it almost looks like a hydraulic lift. it shakes the snott out of the vehicle. sometimes the frames are held in place and just the suspension moves. it just depends on the components being tested.
the shock mount coming off is because of the force not pulling straight down it follows an arc.
the path of the front suspension is designed in a small portion of the arc and the movement of the shock is linear. now we are faced with a problem. i know there are bushings at the end of the shocks but that only helps out a little.
the upper shock mount on the truck is welded from underneath. the shocks on the truck are a bayonette upper. the upper is a shaft and not a bowtie like most older shocks. when the suspension goes past full rebound it uses the upper shock shaft as a lever and it multiplies the forces by X amount. it is like prying off an old pop bottle cap. usually the shocks have a little extra room in them. it is just enough to stop from damaging it.
the shock is not used as a travel limiter. the frame at the top is used, but the lower control arm has no limiter and can over articulate with a longer shock.
the lift kit won't over articulate the control arms because the kit is actually keeping the original suspension travel except for the axle shaft angle is changed (knuckle lift ones).
if the longer shock is in place then in full jounce (compression) you will damage the shock. the mount should take the punishment because the mount is actually on the bottom and side of the frame rail like an L.
if you take a closer look at the shocks you would see that they aren't tack welded anymore. the weld should go all the way around. at least the tenneco's do. (monroe's, rancho's and whatever else they produce).
most of the test here push the 100,000 mile envelope in just a few months. i have seen them testing engines at full power non stop until it blows up. then they try to figure out what was the failure and then look for a remedy. then repete the whole process. the suspension tests are done the same way.
like i said before real world and GM testing are not the same thing. the GM testing is way more severe because of legality.
Here is complete info. on GM snowplow prep package.
https://www.gmupfitter.com/secure/html/publicat/bull/bull27.pdf
Superlift does not increase the track width. They use the factory A-arms and everything. It is actually very similar to the Pro Comp lift.
I agree with you on selecting the appropriate rim. I'm running 265's on the stock rims, but am not keen on the idea of 285's on stock rims. For 35's, we always ran them on 8's for offroading - but that's a different application. If memory serves, an 8.5 is acceptable, but agreed, 10's will be better.
Originally posted by afp:
Does the Superlift increase the track width? [...] I would insist on 10" rims with the 35's because I will be trailering with this rig, and I want a stable ride when towing. A 35" tire on an 8" rim would allow the side walls to roll a bit. Thanks again, Jobbie. I can see how the 4 poster suspension tester cool machine :D could/will push the suspension past what virtually anyone is going to do, and lead to breaking parts sooner.
--Rob
After cranking the torsion bars, and using stock aftermarket shocks like Rancho or Bilsteins...does not putting a spacer on the top shock bracket create more chance of compression and consequential leaking (@ blowing up) when hitting a large pothole on a logging road at 50 mph? :confused:
It seems to me that I might be better off not putting any spacer on at all since there will probably be much less stress on an extended wheel where the shock is at its longest compared to a lifted wheel (when pushed up by an obstruction) which would tend to overcompress an already slightly compressed shock.
Also, if I am able to move my bumper stops down, then I will also be able to limit my shock extension...right?
So...am I best off not putting in a spacer on my front shocks when raising the truck by 2" and instead just lower the bumper stops?
Whats the concensus out there on this?
Many thanks guys... smile.gif
Sorry...mistake on the last post... :eek:
I meant if I lower my bumper stops by 1" (or more if I can), then I should be able to limit my shock "compression" when I hit hard.
So what does the jury say about putting a 1" spacer in the top of the front shock mount such as what "afg" did if I am able to lower the bumper stops?
TH,
you do have a better chance of (blowing up) your shock at "compression" with the shock spacer. with the shock spacer you have the chance of over extending the upper ball joint. :eek: but also if there is no shock spacer you are at risk of bending the shock bayonette. technically it would be safer to not put the shock spacer in.
just move the auxiliary spring. you would need to know how much you lifted the truck from a point on the frame to a point on the lower control arm.
take a measurement at stock then after the lift.
that should be a close figure for you.
Many thanks to all of you for your advice! smile.gif Got the lift done on Friday and went well. Truck is up 2" in the front and I put 2 1/2" riser blocks on the rear. Drives just fine...feels awesome! Slightly stiffer ride but still very nice.
If anyone needs some specifics then please feel free to email me and we can go over things.
Bottom line....$CAN 300 labour to raise the front and rear plus do some other special modifications to suit my particular needs. $75 for two new keys. Plus cost of new U bolts, riser blocks and four new Rancho 9000RX shocks. Shocks cost quite a bit :eek: !
Cool!
I still need relocate my bump stops--ocassionally the tires will rub. For example, if I am going over a transition form a med steepness downslope to level and i apply the bakes at just the wrong time, the tires will rub momentarily.
Eventually I'll need the lift............
Blaine
I am going to lower my bump stop springs. They need to go down about 1/2" to get them back where they were stock.
Today I saw a stock DMax with 245s with his wheel turned about 3/4 of the way. He only had about an inch of clearance from the tire to the aft inner portion of the wheel well. My truck with 285s and raised 2" has the same amount of clearance.
I have had rubbing under the conditions I described in my last post. Well, if the stock DMax has the same clearance as I now have and the don't have any rub problems, then I need to get my bump stop springs back in contact with the lower A-Arms. Maybe this will prevent the tires from rubbing.
Blaine
Jobbie, my dealer didn't have a problem replacing my upper A-arm because of a torn ball joint boot complete with H2's and green keys. They wouldn't cover an alignment under warranty because of the keys. I didn't fight that one...save that for a really big problem.
I got the bump stop springs down 1/8", and I need to go about 1/2". I'll need to fabricate spacers, and will have to make provision for the little protrusion that keeps them from turning as you install them and when they are in place.
Blaine
Mike330R
01-22-2004, 08:32
I plan on installing an RCD lift w/ Micky Thompson Wheels and 35" tires.
Anyone else running an RCD?
Reading through these forums it seems most people here don't have or want lifts. Is there a reason?
Thanks for any info!
What does "RCD" stand for?
Blaine
Mike330R
01-22-2004, 21:47
Race Car Dynamics
www.racecardynamics.com (http://www.racecardynamics.com)
Originally posted by Mike330R:
Reading through these forums it seems most people here don't have or want lifts. Is there a reason?
I can't talk for other people, but I came *real* close to putting a 6" lift on mine (ProComp). In the end, I decided against it for a couple reasons:
- I've already got a play-toy: http://www.bc4x4.com/fv/2002/hulk/
- steering parts seem to be notoriously weak and heavy tires with more leverage will only make things worse.
- I work this truck, and put on a lot of miles (30k+ miles/year). I don't feel like lifting T-cases and axles up another 8-9 inches into the back of the truck, dealing with poorer economy.
- with the lift, there's *always* extra expenses - replacement costs for tires, new wheels, etc.
I'm still debating over a mild 2" lift. Saw one and got to drive it (TH's) and loved it. And I could still "work" the truck.
--Rob
Mike330R
01-23-2004, 15:58
Rob,
Nice Blazer!
You have some good points. I plan on the RCD kit. I will have to keep an eye on teh steering parts but I was expecting that.
I imagine the pitman arm will be teh 1st to go?
Got the work done. Truck runs great smile.gif with one small problem :eek: .
When going over a sharp, high angle speed bump (at low speed), there is a small thump once I'm at the the top of the speed bump. It seems that there is a small bracket that looks like it acts like a stop of some kind. Its hitting. A mechanic told me that this stop acts to prevent the suspension from overextending and causing ball joint problems. He said it isn't a big deal and its doing what its supposed to do.
What seems to be happening is the tires hit the bump, have lots of free upward travel but then the rest of the suspension catches up and travels up on the rebound and thats when the stop bracket comes into play.
This stop bracket is located just below the rear arm of a large "U" shaped suspension arm.
Any thoughts anyone?
Are you referring to the bump stop springs?
No Blaine...what seems to be hitting is a small metal protrusion located just below the rear arm of the large U shaped suspension piece (the shocks go right thru the middle of it). Least thats what the mechs say.
I'll have to take a closer look. I didn't get my bump stop spacers made this weekend, so i wasn't even under the truck.
I wonder if lowering the bump stops has caused this problem? If you haven't experienced it and you raised your truck 2.5" (mine is 2.25") then the cause might be the bump stops being lowered. If they are lowered, then there is less opportunity for suspension travel on the up swing (I think).
So maybe leaving the bump stops as stock would be better.
What do you think?
I now have my truck at 2". I occasionally rub, like when braking and turning through a dip, so I am hoping lowering the bump stops will stop that. I have noticed that on stock trucks, the bump stops seem to be touching when the suspension is "at rest". While lowering the bump stops on a raised truck will limit it's travel, it won't be any less than stock.
How are your bump stop spacers made?
Blaine
I wasn't there to see it but all they said they did was to weld 1/2" steel between the existing metal and the hard rubber (or whatever it is). I assume that they drilled a hole thru it to fit a bolt.
afg...talked to the mech who lowered my bumper springs. He says he just inserted a metal spacer after drilling a hole thru it. He countersunk the bolt on the bumper spring and then welded that to the spacer. I may have lost something in translation...does that make sense to you? :confused:
Just to let everyone know....I am very happy with the torsion bar crank with green keys .... 2.25" gain. Ride was slightly harsher that stock but still good. smile.gif
However, I just switched from 245/75R16 tires to Dunlop RVXT 255/85R16 using my stock 6.5" rims. The taller sidewall has given me back my stock ride...incredible and very happy. :D
Had the tires for just two days...got caught unawares and went thru some very slick black ice this morning :eek: ...no problems. :D
Yellow '03 H.D.
02-18-2004, 20:01
All "Spindle type" lifts are a 4" lift that uses a drop knuckle that creates a harsh C.V. angle.
Trust me on this, a lot of companies advertise their lift as an 6" lift, the differential is only dropped 4" while the spindle is dropped 6" which creates a harsh angle on the C.V.
I would avoid all spindle lifts from my experience. Unless you want to crank it down and keep it at 4" where your c.v.'s are parallel to the ground, ( which is the way G.M. designed your truck to function)
Yellow,
These HD spindle kits are true 6" lifts, with the CV Axles at the factory angle.
However, I understand that some of the older IFS lift kits were as you describe.
Blaine
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