need axle advice

[flomulgator]

So I searched and I searched and now I'm just gonna ask.

My ride is a 1991 V1500 Sub with a corporate 10 bolt, 8.5" axle. The rig is a 6.5TD (actually a 6.5 repower of a 6.2 setup with a Banks turbo, but I digress)

I need to swap out the F&R ring an pinion, because the truck shifts all wonky. I've got a 3.42 gear ratio and 33" tires, and the resulting RPMs are too low. This is causing issues with turbo engagement, which in turn is causing problems with excess heat generation. Also, the transmission has shifting conniptions because the gears are spaced too long. I found that 3.90 gears will get me exactly back to the stock design range for RPMs, but again, I digress.

So I'm about to order my R&P when I start thinking about axles. I've got the 10 bolt on larger tires and a new shiny snail adding 100 torques. May get a tiny lift if I replace the gawdawful springs. May also tow a small weight on rare occasions (<4000#). Is the 10 bolt up to the task long term? If not what should I get? Most importantly, I could not find reliable information on what bolts on to the truck, what requires another part or two, and what requires major modification. Here are some options:

Corporate 12 Bolt
Dana 60
Corporate 14 Bolt
Stuff off old '70s trucks

I've found some good deals on used stuff locally, where I could get either 3 of those with things like disc brakes or a posi/locker already installed, usually in either 3.73 or 4.11 gear ratios. Lot of added bonuses there. I really want a traction device in the rear because I do a lot of highway driving in mixed snow, where 4WD is not practical poor road conditions develop faster than I can reach to the floor.
Side question: Anyone have any experience with an auto locker in the snow?

I only want to purchase something like this though if it's going to be relatively simple. If the 10 bolt is strong enough to last me, I'd prefer to not even bother. Last question: Is it possible to find out the spline count on a 10-bolt without pulling it apart? Cuzidonwana

[More Power]

Aside from changing the R&P ratio, I'd leave the front axle alone. For the rear, the GM 9-1/2" 14-bolt semi floater would be a good choice, and it would allow maintaining the 6-bolt lug axles.

The rear 10.5" GM 8-lug axle wouldn't make sense unless you were planning to use the burb to rock-crawl.

You can read more about the 9-1/2" and an Eaton posi at the following link:
http://www.thedieselpage.com/reviews/randys.htm

Now... The Banks turbocharger is non-wastegated and slow to spool, meaning the real power is in the 2500-3000 rpm range. For those who run at 1800-2000 rpm range looking for mpgs, there are better turbo choices.

Jim

[flomulgator]

Aside from changing the R&P ratio, I'd leave the front axle alone. For the rear, the GM 9-1/2" 14-bolt semi floater would be a good choice, and it would allow maintaining the 6-bolt lug axles.

The rear 10.5" GM 8-lug axle wouldn't make sense unless you were planning to use the burb to rock-crawl.

You can read more about the 9-1/2" and an Eaton posi at the following link:
http://www.thedieselpage.com/reviews/randys.htm

Now... The Banks turbocharger is non-wastegated and slow to spool, meaning the real power is in the 2500-3000 rpm range. For those who run at 1800-2000 rpm range looking for mpgs, there are better turbo choices.

Jim

Yeah, I wasn't planning on messing with the front. I just don't go into 4WD that often, and when I do I'm not railing on it and I'm certainly not towing at speed. Just a gear swap up there.

Thanks for the article. Really I should drive up to Everett and check that place out. Thanks for the suggestion of a 9.5" 14 bolt. Is it a direct swap or what does a swap entail? I'm gathering from your suggestion that the 10 bolt won't cut it for long term durability with a turbo?

I am learning the hard way that Banks could really use a wastegate. Right now my problem is that boost is non-existent unless I'm flooring it, but with the fuel rate turned way up and the RPMs down, my AFR is ugly and my EGTs climb dangerously high. I backed off the fuel a 1/10th of a turn and put in a high-flow T-stat, but the gearing is the real culprit. Just installed a Tiny-Tach (great, BTW) and found my RPMs to be 1600 @ 65mph...way too low for even normal operation. My target is 1800 @ 65mph in OD and 3.90 hits the mark perfectly (which means OE did too). According to your article in 6.2 Vol. II that's the sweet spot for economy and torque, and Banks says that about there is where EGTs should be ~400 deg w/ 2lbs. boost (I'm currently 0.5 # @ 65 mph). From there a downshift will really light up the turbo too.

Gah, too much coffee, too verbose, back on topic. 3.90 is a custom size so if I buy a used axle it will have to be 3.73 (a bit low) or 4.10 (a bit high). With the way my setup works, I'm favoring a bit high. Lots of Dana 60s come that way, and many are available. It appears 14 bolts often come with 3.73. But again, I don't know what kind of work goes into these axle swaps.

[More Power]

Yeah, I wasn't planning on messing with the front. I just don't go into 4WD that often, and when I do I'm not railing on it and I'm certainly not towing at speed. Just a gear swap up there.

Thanks for the article. Really I should drive up to Everett and check that place out. Thanks for the suggestion of a 9.5" 14 bolt. Is it a direct swap or what does a swap entail? I'm gathering from your suggestion that the 10 bolt won't cut it for long term durability with a turbo?

I am learning the hard way that Banks could really use a wastegate. Right now my problem is that boost is non-existent unless I'm flooring it, but with the fuel rate turned way up and the RPMs down, my AFR is ugly and my EGTs climb dangerously high. I backed off the fuel a 1/10th of a turn and put in a high-flow T-stat, but the gearing is the real culprit. Just installed a Tiny-Tach (great, BTW) and found my RPMs to be 1600 @ 65mph...way too low for even normal operation. My target is 1800 @ 65mph in OD and 3.90 hits the mark perfectly (which means OE did too). According to your article in 6.2 Vol. II that's the sweet spot for economy and torque, and Banks says that about there is where EGTs should be ~400 deg w/ 2lbs. boost (I'm currently 0.5 # @ 65 mph). From there a downshift will really light up the turbo too.

Gah, too much coffee, too verbose, back on topic. 3.90 is a custom size so if I buy a used axle it will have to be 3.73 (a bit low) or 4.10 (a bit high). With the way my setup works, I'm favoring a bit high. Lots of Dana 60s come that way, and many are available. It appears 14 bolts often come with 3.73. But again, I don't know what kind of work goes into these axle swaps.

According to Jim Allen's recent book entitled "Differentials", the GM 9.5 appeared in the 1981 in C/K 20/30 pickups, Suburbans and vans - meaning they'll require 8-hole wheels. According to Randy's, 3.23, 3.42, 3.73, 4.10 and 4.56 are the available ratios. These 80's axles would be a bolt-on for your half ton, but the 8-lug thing might be a problem.

Beginning in 1988, GM installed the 9.5 in their 1/2-ton trucks, but the hub to hub width changed, as did the spring perch locations. So... A custom axle might be within the realm of possibility, using a 1981+ 9.5 with custom 6-lug axles.

Now... the GM 10-bolt is stronger than you might think. I put more than 400-hp to one in my Duramax powered 1989 Chevy before swapping in a custom 9.5. I didn't break it even though it was equipped with a posi. Where the 10-bolt falls down is grueling mile after mile under a hard load - like heavy towing. That's partly why current diesel pickups are using an 11.5" AAM rear diff.

I actually spoke to Gale Banks about the slow spooling Sidewinder used in their 6.2 kit. His reply was (and it does make sense) that "power is there when you need it". I suppose this means that a downshift and more fuel will spool the turbo and make the right amount of boost. Unfortunately, tooling around at low rpm and low throttle means there's no or very little boost, and that boost won't rise much till you get a downshift with more pedal.

Gale suggested I try their turbo produced for their 7.3L IDI kit. I would add the Holset HX35W (like that used on the 1994-97 Dodge Cummins) to that recommendation. The Holset is a wastegated turbo that should fit the Banks manifold without a lot of fuss. The factory 6.5 turbo would also be sized about perfectly for the 6.2, but the exhaust outlet won't fit the installation with any grace.

Jim

[flomulgator]

Thank You!
I can't stress enough how valuable information like this is. Possessing only hand tools and limited funds (and knowledge), I don't want to get into custom axle or mount work. But I also wanted to avoid building up an axle with a posi and new parts only to have to throw all that time & $$ away when the axle broke or proved inadequate.

We basically got the turbo for the big grades we encounter out west, especially when we are tooling around the Rockies at altitude. The Banks does a good job of this. Also to be able to pull off passes on 2-lanes around the 5-under drivers that plague Washington's highways. Even fully lit, the turbo only produces < 400 lb/ft so I think even if I was towing something moderate on a grade it wouldn't compare to a Duramax @ 700lb/ft or as you said, heavy towing. Any guidelines on how much weight does start causing problems?

I'll give the bolt-on 80's 14 bolt (w/ wheel swap) some consideration but will likely stay with the 10 bolt. Again, thanks!

turbo geeking tangent:
I think the Banks was styled that way because it gave the biggest possible numbers that look good for marketing. I've got a turbocharged sporty gas car as my DD, so I'm a bit familiar with turbo selection. In the sport world people choose huge turbos that only kick on right near redline (due to very high flow/spooling requirements) but then produce stupendous power. Taken to the extreme, this produces cars known as "dyno queens" cars with turbos so powerful that they are undriveable. They produce 1000hp or whatever on the dyno but going from 150 to 800 hp in the space of 200rpm @ WOT produces uncontrollable wheelspin....so they aren't actually drivable!
Anyways this relates to Banks in that I think they wanted to post some good numbers in a difficult application. So they chose a larger than necessary turbo with a high flow requirement. As you pointed out, a lack of wastegating compounds the issue. There are 3 ways to improve the situation:
1. Smaller turbo. Most non-sporty turbo cars go this route because it is a very driveable setup. Minimal turbo lag, just feels like more cylinders. Some diesels have too (I believe early 12v Cummins and TDI VW's). However, don't post big numbers and run out of breath before the engine does.

2. Sequential turbos (as opposed to twin). One small and one large, best of both worlds. E.G. RX-7, 300zx, etc...

3. Variable Vane Geometry Turbos. Using technology invented by Honeywell for the high-bypass turbofan in aviation, they can change the effective size of the exhaust housing. Pretty cool, very expensive, and currently used by all diesel engines for all makes sold in the US, IIRC.

Anyways, I'm still trying to learn more about wastegating as it applies to flow rates but it clearly has an effect. I read an article that used the banks kit but substituted the Ford IDI Banks turbo like you mentioned for the same reasons. Unfortunately they didn't get into drivability or do much post-analysis after the install. After a long line of other chassis upgrades though I would consider a turbo swap.

/turbo rant

[87max]

From my experience a 14 bolt 10.5 full floater is the only way to go. the semi floaters were known for occasional problems. Go with 4.10's the difference is so minimal it's not worth even doing the math. The beauty of the 14 bolt is they are available in a variety of apps, vans, 2wd, 4wd, 3/4 1ton etc.. check your spring perch location (width) for alignment & find the 14 bolt for you. Detroit lockers are the bomb in that axle you can do it yourself, the carrier gets reused unlike other axles you only replace the spiders and (cross) that's why they are several hundred less for the 14 bolt full floater. Enough savings to buy the axle. I used to run a 14 bolt in the back and a 10 bolt up front. I had 6 lug up front and 8 in the back it's not a crime to do that! I would put about 800 pds in the back and plowed in 2wd most of the time.

[AJMBLAZER]

1991 will have a 30 spline rear axle unless someone pulled it and swapped it for some reason. 1989 was the first year the rear 10 bolts got 30 spline axleshafts. Makes them about as strong as a 12 bolt. Bit iffy for a Burb that will see some decent towing.

I'd say 3.73's will get you better mpg and 4.10's will get you more low speed driving torque.

Little late to the party but I'd suggest either a 6 lug 14SF swap out of a K2500LD from the next body style or a whole 3/4 ton axle swap.

Swapping in a 14SF from the newer body style just requires a competent welder and someone good with a grinder or a plasma cutter. Remove the spring pads and shock mounts and have them reinstalled in the correct locations. Might need some rear driveshaft mods and there is a conversion rear axle u-joint for doing this.
MAKE SURE YOU FIND ONE OUT OF A 4X4! The 2wds had a narrower rear axle than the 4x4's.


Either that...or do a whole 3/4 ton axle swap. I've seen matching sets of 4.10 geared rear axles go for under $400. 73-87(91) 3/4 ton axles would bolt into your truck.

[flomulgator]

Okay It's been awhile but it took me about that long to decide on what I wanted, build funds, etc. Here's what I've ended up doing.

1985 K20 3/4 ton full axle swap.
This ends up being a front, 10 bolt, 8.5" open diff axle with 4.10 gearing and 8 lug hubs
Rear 14 bolt, 9.5", semi-floating Gov-lock (LSD) diff, 4.10 gearing, 8 lug hubs on large drums.

Cost me $400 used, which seemed reasonable after researching my local market.
Here's what led me to the decision (to aid others):
Changing gears on my stock axles to 3.90 would have cost be about $1100 in the end, after factoring in the tools I didn't yet have (hydraulic press). This price included an Auburn/Eaton positraction diff that i wanted. However, unlike just wrenching in some axles there appeared to be a good bit of measuring, feeler gauging, and other stuff that could go wrong. And I have the same axles still.

With the swap I get the beefy rear axle, and everything's already installed. Added bonus is a decent increase in rear end braking power, judging by the signficant increase in rear hub size. The downside is, yes, I had to buy brand new 16" 8 lug wheels and tires to match. I looked into 6 lug 14 bolts but they are, at this point, insanely rare (nonexistent locally, only nationally available). I looked into 15" 8 lugs but they are really designed for jeeps and upon digging found that the load rating is inadequate for a full size truck/suburban. I emphasize that because the information is really buried and that's pretty important. So 16" it is, and had to be new because all the wheels on the used market were off newer trucks with a very positive offset (would pull the wheels in and reduce track width on older trucks). There were a couple correct-offset old style CL wheels but they were rusted and BUTT UGLY.

So I take a loss on the wheels. Turns out my tires only had 30% tread left anyways and as I need them for traction, not just road legality they were pretty shot for my purposes so I am not really losing much on buying new tires (M/Ts that're gunna be suuweeeet!). So that's the math and technical reasons that led me there. It took a lot of research and running numbers so I hope that helps someone else. 1985, as noted by others, should be a direct bolt on. I've cleaned and painted them but have not yet thrown them on the truck (that's today's project!). I'll post back only if there are hiccups.

Between the "HD" intake manifold and the full 3/4 ton axle swap I'm 2 shocks and some springs away from driving the mythical V2500 diesel suburban. Time for a rebadge!!

[AJMBLAZER]

Sounds good man. Most 15" tires are a load range C which is iffy for any kind of heavy towing. Folks just don't realize that. I put 16" tires on The Blazer just because I liked the higher load range and taller/narrower tires were more common.

FYI you don't need dual front shocks. Just put some good aftermarket singles up front and the duals will be irrelevant. Those are from the days when shock technology wasn't near what is has been even on the bargain basement aftermarket shocks. Just compare the difference in body and piston size between a set of Rancho/Superlift/Tuff Country/Skyjacker/etc shocks and some ACDelco replacement shocks.

[flomulgator]

Good to know about the shocks. I wasn't so much worried about the C load tires (old were C, now have E) as the wheels. The 15" 8 lug wheels I found were usually 1600lbs/wheel, which only totals 6400lbs . The GVWR on my V1500 sub is 7300lbs! I found one set 1800/wheel (still no thanks) and some others that were unlisted (also not buying). I don't know what a taco'd truck wheel looks like but I don't want to find out!

[AJMBLAZER]

Kinda like an oval...ask me how I know.


Good point there as well. I had the factory 15x8 Rally's so I wasn't too worried about their strength but yes, aftermarket is pretty skeevy sometimes.
My aluminum 16x8's are rated at something like 2000lbs or more. More than enough for my Blazer.

[flomulgator]

Factory 15x8s ??!!

Unless you were being rhetorical I'll bite, how do you know? Got pics? Bonus points if the story started with "hold my beer" or "check this out!"

[AJMBLAZER]

Yep, the factory fancy Rally wheel on these were 15x8's:


15x8 with 4" of backspacing.

You can verify it by using Car-Part's Holman interchange.
http://www.car-part.com/cgi-bin/search.cgi

[87max]

Don't forget as you go up in load rating on your tires they typically have a harder compound, hence come winter they won't be quite as nice on the ice as the softer "c" that you had before.

[AJMBLAZER]

Modern compounds, designs and lots of siping counteract that completely now-a-days.

Been running D and E load range mud tires on stuff as small as a Suzuki XL7 for years now and had no troubles even during 6 Northern Michigan winters.

[DmaxMaverick]

I have two 5-wheel sets of the OEM steel/rally 15x8's. None of them are round anymore, and not one will balance a tire. I tried several brands of steel wheels over the years, and all of the 6 lug 15x8 steels were no longer round after about 75K miles. Even the "heavy duty" wheels. Eventually, I just settled on buying cheap steels every 75K, rather than trying to find a permanent solution. There was no permanent solution I could find, and the cheaper wheels were as good, or better, than the fancy wheels, and even the HD's. By cheaper, I mean store overstocks and clearance sales, not "cheap made". None of them were underrated for the loads they saw, and often were up to and touching that limit.

[Robyn]

I have always tossed the steel wheels on my rigs and ran aluminum wheels.

Never had any issues for the most part.

Did blow a tire once way out in the sticks and crunched the aluminum wheel pretty bad on a rock.

My 89 K5 has some nice 15 X 10 alloys on it now.

Have another set of alloys for the project K5

I agree though, if you are going to pull heavy or ??? the 16 inchers with the heavy axles are far better.

I have seen several K5's with 3/4 ton axles around here.

A Burb with 1/2 ton axles is just too light other than as a people mover.

Missy

[flomulgator]

Oh sorry, I got myself confused AJ. I was thinking 15" dia. by 8 lug. THAT would've been crazy from the factory. I ditched my stocks years ago for a 15x8 6 lug and now it's a 16x8 8 lug.

Missy, the sub usually just hauls people but may haul light to medium to heavy boats in the future (in that chronological order) so it's reassuring to have the heavy axle. It sounds like the 10 bolt 30 spline would've been up to the task, but I'm excited about the increase in braking power more than anything. The difference in hub size is substantial.

Getting those U-bolt nuts off was the toughest nut to crack I've ever encountered. Was using a torque bar for the leverage at one point and snapped the scale clean off because I was somewhere around 200 ft/lbs according to the indicator rod hanging in free space (blow torched, PB blasted, and full, bouncing body weight). I actually destroyed the threads completely in one area due to heat/pressure. And they were awful all the way out. Air impact wrench on max was useless. Other side I said "screw it" and busted out the 2KW angle grinder and put on a light show. That worked

Comparison pic

[flomulgator]

Okay so I've ran into a major hurdle, right at the end. My driveshaft U joint won't hook up (I thought this job was a bolt-on??). Wondering what was wrong, I measured the two female ends and sure enough, they are slightly different between the 10 bolt and the 14 bolt. The U joint is just a bit too long, but other wise fits fine.

Looking around it appears the receiving end is called a Pinion Yoke?
So here's the question: Does the one from the 10 bolt fit onto the 14 bolt, aka, can I just swap in the old part?
Or do I need to go buy a different U-joint piece?
If I need to get a piece would the correct U-joint come off the driveshaft the 14 bolt axle was connected to and would that work on my 1500 driveshaft? (also known as the Junkyard Question)

[Yukon6.2]

Hi
Find a parts store that has a experianced parts guy,or a store that deals with u joints and drivelines.There are offset ujoints that should fit both your new axle and old drive shaft.Might take a little digging if you don't find a parts guy who knows about them.
Good Luck Thomas