taller gearing

[Keith Richards]

I am considering 3.42 gearing for my 4.10 geared hd truck.I do alot of towing,(small to big trailers)and heavy hauling, and the gearing only seems to suit me when I'm at,or above 8600 lbs.Am I going to be doing more harm than good?I like the torque but cant stand the high rpm's.How much $$$ will this cost to have installed.Any advice is appreciated.

[john8662]

From pulling with my 6.5 4x4 suburban geared 4.10 I really think that the 6.5 needs the 4.10 if you're pulling a real load. I put an older 6.2 4x4 suburban on a car trailer and towed 500 miles with mine bucking the wind most of the way, The 4.10's helped alot, as I just left the transmission in OD the whole time, except when in stop and go city areas. I wouldn't change the gears if you pull a lot. If you want to change the gear ratio still, go with 3.73, but you won't gain too much.

[DA BIG ONE]

Well, I had mine done from 4.10 to 3.42 about a month ago, cost just under $1,500., and because I have been having speedo calibration problems fuel milage actually went down a few mpg across the board!

I had found out the Jet peformance calibration options would not work with my truck, and hoping another companies unit will, but do not know yet.
Jet claims their VSSB unit will not work at all, then their SCU2000 did calibrate the speedo but caused real hard shifting, and when I would try to stop I would get a severe shudder like the converter was still locked, and the engine rpm's would start to rise by itself after stopped.
&^%#()*& way to find out after the ratio change.

In reality, this truck has been a nightmare since the ratio change!

My truck is a 1999 GMC SUBURBAN 2500, 6.5 TD, intercooled, freeflow exhaust used to get 18 mpg on the highway......

[tanker]

Keith why not go with taller tires, and/or a "Gear Vendors" overdrive, then you would have a choice. I have 3:73's and sometimes wish for 4:10's, but the 3:73 ratio seems to be a good all round number. If towing with anything higher would cause a lot of lugging in my opinion.
If you were not to tow, then I give my thumbs up, better mpg etc. smile.gif

[Scooby]

Kieth, I have done quite a bit of gear changing in my hobby of playin in the mud. Personally, I have never gone higher in ratio, only lower. I know you dont want to see those high rpm's all the time. I don't know if you would consider this, but what about going to a taller tire?? Small changes in tire diameter make a big difference in road speed vs. rpm. I have had real fun getting speedometers to read right again on old mechanical systems after changing tire sizes.
Here is a link to 4 wheel parts gear ratio guide. Disregard the color coding as it is for gas engines.
http://www.4wheelparts.com/Tirel_gear_ratio.asp
Many of the gear vendors have charts also. Try Randy's ring & pinion (ringpinion.com).
Another suggestion- If you do decide to change ratios, I always do the rear first, then drive a while- not engaging 4WD of course, just to see if I really want the ratio I think I want. You can only do this if your front end is completely disconnected in 2WD. I have not worked on IFS trucks like the newer Chevy's- only solid front axles- so ask if you can run your truck like that to check your selection. If you arent changing the gears yourself, most of the cost is labor. I would consider tire size change as a less expensive, and more easily reversible fix, as long as you have clearance.

[Shotuscnc]

just changed gears in my 2wd suburban.. from 3.73 to 3.21 I do no towing and have seen no improvement in fuel economy with mixed driving.. tho i do appreciate lower rpm when cruising... this allows a cruise at 75mph and maintain reasonable fuel consumption.. the change was straight-forward and VSSB was easy once I had the good info on 14-jumper configuration. I kept the 3.73 gears with pinion bearing installed so that a reverse swap will be easy enough should i begin towing.

[JohnC]

I had a '93 with 3.42 gears and a standard trans. We towed a horse trailer that weighed in around 5000# and was pretty aerodynamic. We got great mileage but the performance was boarderline. I think it would have been a lot better with an automatic. One of the problems with the stick was the distance between gears. If I had it to do over, I'd go with the 3.73. Now I'm pulling with a heavier truck, automatic and 3.73 and I'm happy... smile.gif

[Marty Lau]

Keith;

I changed over at about 36,000 miles from 3:73 to 3:42 I have 166,000 now. I tow 5,000 lbs 3-4 days aweek that pull easier than my camper at about 3,500lbs. (15ft) I have pulled 25-27foot bumper pull campers through the rockies for a couple over 1,000 mile plus pulls and have pulled 10,000lb water trailer. I try and pull the big water tailer as little as posible it's bit much. If you pull a lot at the 8,000 lbs plus I'd be inclined to go 3:73 if most your towing is less say under 6,000lbs and once in awhile at the heavier weight then I'd go 3.42. I'd say you should also consider the types of trailers you tow are they higher profile with more wind drag or more areodynamic? At heavier weights I just run slower in 3rd it's also easier stop a heavey load from 50-55mph than say 65mph+, my real heavy pulls are short runs under 20 miles so 10-15 mph doesn't add much to the trip.

In 3rd lockup at 55mph the rpms are close to a 4.10 in OD lockup at 60mph. I would say excpect to pay $700-$900 per axel. only 1 with 4x2: :D

[Keith Richards]

Very helpfull advice,thanks guys.I would love to go to a taller tire size,I already have(i think)as tall as I can fit without trimming fenders or a lift.Dont want to raise torsion bars.Maybe a lift in the future.Hearing all the headaches with lowering I guess I should be happy with my gearing.Ill just look forward to a lift in the future,or my real wish,a dana 60 under the front"ROOOAR!"

[Scooby]

I built and put a DANA 60 in the front of my 83 K2500 mud truck. It is a great axle. No failure yet, but I suspect I will eventually break the axle shafts, as I chose to use the stock shafts when rebuilding due to lack of funds !! I will upgrade after parts break. I also put in a Detroit locker with the 4.88 gears. Pulls great.

[Diesel Dan]

I replaced the 4.10 from my '89 crewcab with a 3.36 gear. It had the TBI 454/th400 combo. Biggest reason I wouldn't do it again was acceleration from a standing start. Very hard on the trans with a heavy trailer. I had a '93 K2500 with 6.5TD/NV4500/3.42s, the manual made up for the tall gears on take-off.

Also had a '88 V30 crewcab with 6.2/th400/4.10s. Installed a Gear Vendors OD, that was the way too go :D ! Good off the line and decent RPMs, compared to no OD. On my gas powered '89 CC I didn't really see any MPG change either, maybe +1mpg. Took way more throttle to get the load moving.

My recomendation for towing: no taller than 3.73s, 4.10s or 4.56s with add on OD with 4L80E would be ideal. IMO.

[Diesel Dan]

Forgot to mention, had a '90 dodge CTD/auto with 3.07s. Even with way more grunt of the cummins it couldn't offset the tall gearing for break away power.

[Keith Richards]

Diesel dan, I have had ,and am still very interested in classic (80's)hd chevy pickups.What exactly is a v-model pickup?Just curious.

[Diesel Dan]

The old body style was still available from '88-91 in crewcabs, blazers, suburbans and chassis/cabs. The new style is C/K and the old is R/V. R=2wd, V=4wd.

[DA BIG ONE]

I found that my turbo boost circuit was not working properly, fixed the boost problem and now get 21+ mpg @ 70 mph, so my gear change front and back from 4.10's to 3.42's now shows good results.

[CleviteKid]

In 1987 Chevy and GMC got stupid and abandoned the valuable C-K designation for 2WD and 4WD trucks, and replaced it with the R-V designation, where R = C, and V = K. Sort of a New Coke must be better than Classic Coke kind of thing. This carried thru with the older body style on Suburbans and Crew Cabs ( and Blazers, I think) thru 1991. The general public did not know or care, and the enthusiasts (that's us) just got ticked off. Dumb General.

Interestingly, within GM they were always referred to as C-K trucks, even when the R-V nomenclature was official :rolleyes: .

Dr. Lee :cool:

[Marty Lau]

Originally posted by DA BIG ONE:
I found that my turbo boost circuit was not working properly, fixed the boost problem and now get 21+ mpg @ 70 mph, so my gear change front and back from 4.10's to 3.42's now shows good results. :D
ALL RIGHT!!!!!
it didn't make much sense to me why you didn't gain anything in the gear change. :cool: :cool:

[computer monkey]

I have been towing my trailer with the new Max-E Torque program from Heath Diesel for a couple of weeks now. Been very happy with it compaired to stock. I have a link to my rig below. The trailer weight empty is 7000lbs and as you can see has a very large wind drag to it. Our Suburban has 3:42 gears. If I have a long hill or high winds I just keep it in third. Here in a little while I'm adding Heath water injection. Having trouble finding a tank that will fit in the 16 wide by 12 deep and 59in long slot that I have in the trailer.

If any one knows a good place to find plastic tanks can you please post here.

Thank you.


Picture of Rig (http://www.n2outdrs.com/engine/rigweb.jpg)

[Marty Lau]

Computer Monkey try this:


Member # 1555

posted March 25, 2004 09:12 AM
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I know its listed as a fuel tank, but check out this.

http://cabelas.com/cabelas/en/templates/pod/horizontal-pod.jhtml?id=0001124&navAction=push&navCount=2&indexId=cat420004&parentId=cat420004&parentType=index&rid=&_DARGS=%2Fcabelas%2 (http://cabelas.com/cabelas/en/templates/pod/horizontal-pod.jhtml?id=0001124&navAction=push&navCount=2&indexId=cat420004&parentId=cat420004&parentType=index&rid=&_DARGS=%2Fcabelas%2) Fen%2Fcommon%2Fcatalog%2Fpod-link.jhtml_A&_DAV=MainCatcat21276

I am thinking about the 600 series 18 callon tank. it even comes with a sending unit!

Tim

[computer monkey]

This is the tank I am looking at
http://www.dyersonline.com/merchant.mvc?Screen=PROD&Product_Code=88-1032&Category_Code=&Search=tank&Offset=&filter_cat=&exclude_word=&the_fieldlist=g.SRCH_CODE%7Cg.SRCH_NAME%7Cg.SR CH_DESC&range_low=&range_high=&dopowersearch=1&SRCH_CATEGORY_HF=&PowerSearch_Begin_Only= (http://www.dyersonline.com/merchant.mvc?Screen=PROD&Product_Code=88-1032&Category_Code=&Search=tank&Offset=&filter_cat=&exclude_word=&the_fieldlist=g.SRCH_CODE%7Cg.SRCH_NAME%7Cg.SRCH_D ESC&range_low=&range_high=&dopowersearch=1&SRCH_CATEGORY_HF=&PowerSearch_Begin_Only=)


I have up to 17in wide and up to 59in long. Still debating on how high it can be. I was wanting at lest 40 gallons.