Gear Install Questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chargedstang89 · 07-22-2003, 11:44 AM

Hey All!

I have 3.08's in my '85 GMC 4x4. I'm running 33" BFG's, so needless to say, my truck has no power pulling trailers, or even going up hills for that matter. I'd like to step up to 3.73's, but have never installed gears before. I can build motors no problem, but haven't ever tried installing gears. I have a friend who has all the dial indicators or whatever you need. I was wondering if anyone has or knows of a place of a good technical write up to install the gears in the rear and FRONT differentials. I plan on putting new bearings and everything in there too.

Josh

ElGracho · 07-22-2003, 01:06 PM

I used the instructions available on the Randy's Ring and Pinion site. They are very comprehensive and very good. Read their entire tech tips section too, there is more info there.

I recently rebuilt my 12 bolt in my 84 with 3.73 gears and a True Trac, works like a champ with no noise. If you take your time and follow the directions to the letter, you CAN do it yourself. Be warned that 'all the dial indicators or whatever' are probably not going to cut it for tools, you really need the right ones.

Here's a link to the Randy's guides: here and here.

MylilBowTie · 07-22-2003, 03:43 PM

If you always run 33s I would get something a little better like 4.11s even with 3 speed trans. Those are some pretty tall tires.

Sumit sell some videos on how to install gears. http://store.summitracing.com/partde...rt=RMG%2DVIDEO

chargedstang89 · 07-22-2003, 03:52 PM

I do always run 33's. Also, I have a 700r4 tranny. It seems like I always have to keep my foot WAY into the throttle when driving...even on flat ground...just to maintain 65-70mph. It also seems like every little slope in the road, my tranny kicks down since i have to open the throttle up so much. I'm thinking that all of this causes my 8mpg gas mileage. That seems horrible for a brand new crate 350, new edelbrock 1904 carb that's tuned, and a 700r4 with 3.08's and 33's. I'm thinking that by putting gears in, I can greatly decrease how wide open i have to keep the throttle while driving and that, in turn, will help my gas mileage. Does that make sense at all????

phantom dually · 07-22-2003, 06:22 PM

I also have 33's on my 94 3/4 ton chevy. It has the 700r4 also. I talked to a gear guy today and he said run a 4.56 at a minimum. The gear for my truck is like $225 or more because it is a 14 bolt rear damn it!!

*mike reeh* · 07-22-2003, 06:43 PM

yes 14 bolt FF gears might be a little more expensive but have you priced a detroit locker for it? cheaaaaaap. cheapest out of all other detroit applications

mike

chargedstang89 · 07-22-2003, 07:13 PM

so do you think my "theory" about actually getting better fuel economy with steeper gears is true?

07-22-2003, 11:44 AM	#1
chargedstang89 Registered User Join Date: Oct 2002 Posts: 90	Gear Install Questions Hey All! I have 3.08's in my '85 GMC 4x4. I'm running 33" BFG's, so needless to say, my truck has no power pulling trailers, or even going up hills for that matter. I'd like to step up to 3.73's, but have never installed gears before. I can build motors no problem, but haven't ever tried installing gears. I have a friend who has all the dial indicators or whatever you need. I was wondering if anyone has or knows of a place of a good technical write up to install the gears in the rear and FRONT differentials. I plan on putting new bearings and everything in there too. Josh

07-22-2003, 01:06 PM	#2
ElGracho Gentleman Jim Driver Join Date: Nov 2002 Location: Poulsbo, WA Posts: 1,553	I used the instructions available on the Randy's Ring and Pinion site. They are very comprehensive and very good. Read their entire tech tips section too, there is more info there. I recently rebuilt my 12 bolt in my 84 with 3.73 gears and a True Trac, works like a champ with no noise. If you take your time and follow the directions to the letter, you CAN do it yourself. Be warned that 'all the dial indicators or whatever' are probably not going to cut it for tools, you really need the right ones. Here's a link to the Randy's guides: here and here. __________________ Joe '75 GMC Gentleman Jim '84 Chev C10 Short Wide - Super duper plain (manual steering, manual brakes, no dome light, no cig lighter) '85 Chev C10 Short Wide - Super plain Vortec 4.8 4L60E trans also: '81 K30, '83 C30 Crew Dually, '84 M1028 CUCV, '85 M1009 CUCV, another '85 C10 SWB, '89 R3500 Flatbed

07-22-2003, 03:43 PM	#3
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	If you always run 33s I would get something a little better like 4.11s even with 3 speed trans. Those are some pretty tall tires. Sumit sell some videos on how to install gears. http://store.summitracing.com/partde...rt=RMG%2DVIDEO __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

07-22-2003, 06:22 PM	#5
phantom dually Project92 SWB stepside Join Date: Feb 2003 Location: Louisville KY Posts: 4,792	I also have 33's on my 94 3/4 ton chevy. It has the 700r4 also. I talked to a gear guy today and he said run a 4.56 at a minimum. The gear for my truck is like $225 or more because it is a 14 bolt rear damn it!! __________________ 92 C1500 stepside 496 Stroker Competiton Engineering Ladder bars/QA1 coilovers. Dana 60 rear with 4.10 gear and posi. Bonspeed Palisade 20x12 in rear w/335/30/20 and 20x8.5 front w/245/40/20. 5/8 drop with Belltech springs/DJM spindles/drop shocks. WWS Progress thread http://67-72chevytrucks.com/vboard/s...d.php?t=140448

07-22-2003, 03:52 PM	#4
chargedstang89 Registered User Join Date: Oct 2002 Posts: 90	I do always run 33's. Also, I have a 700r4 tranny. It seems like I always have to keep my foot WAY into the throttle when driving...even on flat ground...just to maintain 65-70mph. It also seems like every little slope in the road, my tranny kicks down since i have to open the throttle up so much. I'm thinking that all of this causes my 8mpg gas mileage. That seems horrible for a brand new crate 350, new edelbrock 1904 carb that's tuned, and a 700r4 with 3.08's and 33's. I'm thinking that by putting gears in, I can greatly decrease how wide open i have to keep the throttle while driving and that, in turn, will help my gas mileage. Does that make sense at all????

07-22-2003, 06:43 PM	#6
mike reeh 5 day ban, learn to behave. Join Date: Nov 2002 Location: san diego, ca Posts: 683	yes 14 bolt FF gears might be a little more expensive but have you priced a detroit locker for it? cheaaaaaap. cheapest out of all other detroit applications mike

07-22-2003, 07:13 PM	#7
chargedstang89 Registered User Join Date: Oct 2002 Posts: 90	so do you think my "theory" about actually getting better fuel economy with steeper gears is true?



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