What kind of Gears to get?

[chargedstang89]

I'm looking to swap out my factory 3.08 gears. Does anyone have any input on a good set of gears to get? I'm currently running 33" tires with a 700r4 tranny. Have a crate 350 GM Goodwrench engine, but will be putting cam/intake in it. I'm debating between 4.10's and 3.73's. This is mainly a commuter truck, but I tow a ski boat with it in the summer, so I need to keep mileage in consideration. Which do you all think I should get, and what brand of gears? I know certain brands of gears for ford 8.8" rear ends tend to whine. I have a 4x4, so I need to swap out both front/rear gears, and I want her to be quiet/smooth. Also...what size/kind of rear end do these trucks have? I have an '85 gmc k1500 4x4.

-josh

[Mike C]

Do the 4.10s at least. You may even contemplate 4.56 with the OD trans. I did a set of 3.73 in an '87 Blazer with 32" tires, and he regretted not doing the 4.10. He had 3.42 to begin with. Man, your truck must be a DOG in OD with the big tires!

Your truck should have corporate 10 bolts in both ends. This is a good strong rear, at least equal to a 12 bolt, at least in the 88 and up trucks which have 30 spline axles instead of the 28 spline axles. Just don't do hardcore rock climbing or run tires much bigger than you have already.

I have had good results with many different gear sets. I have used Yukon (randy's ring & pinion), Strange, Precision Gear, Richmond, and Motiv.

Check 4 wheel parts wholesalers for package deals. If memory serves, a rear Detroit Locker, front Detroit TruTrac, 2 gear sets and 2 installation sets is $1329 with free freight. They sell Genuine Gear. They sell 2 gear sets and two installation kits for $399.

As far as labor pricing, I charge $150 for a rear gear set in a diff out of the truck, $200 in. $200 for a front out of the vehicle and $250 in. It takes about 4 hours for a rear in a truck and 5 for the front when replacing all of the bearings, seals, gears, and differential.

[chargedstang89]

Thanks for the info. I'll be doing the gears with a friend of mine. He has all of the tools for measuring everything properly and used to install them in high performance cars when he worked at a performance shop. I also need to replace the spider gears in the rear end. Would I be better off just getting a whole new differential in the rear? I have no clue how much spider gears are. I dont' do rock climbing or anything like that with the truck. Mostly highway driving to work and off roading at my friend's farm. You have no clue how much of a DOG my truck is anytime I'm driving. It's horrible on the highway. I have to practically always keep 1/2 throttle just to keep going 65mph and even then, the tranny is always kicking down into 3rd gear and the 4-barrels open. That's where all of my gas goes. The stock 190hp 350 doesn't help either. I need to give her a few more ponies. I'm just looking to get a better seat of the pants feel, as it sits now, towing sucks, and if i nail the truck to pass someone, it's like i'm still standing still.

[kwmech]

A 4.10 gear in an overdrive 700 comes out to about a 3.07 in 4th, and a 4.56 comes out to about 3.42 in 4th. With the 33s I would step down to the 4.56s myself. Have 4.56s in my suburban with 31s and sometimes that is not enough gear.

[Mike C]

If you need spiders for sure I would get a new diff. Tom's Differentials has Eaton posis for the 8.5" 10 bolt for $280, at least the last one I bought was. Cheapest I have found and I am quite impressed. Another thought, a 9.5" semi floater 6 lug 14 bolt is a pretty easy swap and many of them already have 4.10 gears. It is a LOT stronger than the 10 bolt.