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Upgrading Rear Differential?

T

TruckDude94

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Hey y'all,

Well to start off glad I joined here, yall got alot of resources that should prove quite useful. Anyway to the question (btw please forgive me if I sound naive from time to time, I am new to the auto world, and eventually want to go to auto mechanics school to get my education in all this). So I am thinking of changing the rear differential on my 1997 GMC c1500 from a non limited-slip to a positrack. First of all, is this something that I could do with instructions, or would this best be done by a shop? Ill probably go down to a local scrapyard and see if they have anything in good shape. If that fails, where should I look to get a new one? Thanks :)

TD94
 
TruckDude94 said:
Hey y'all,

Well to start off glad I joined here, yall got alot of resources that should prove quite useful. Anyway to the question (btw please forgive me if I sound naive from time to time, I am new to the auto world, and eventually want to go to auto mechanics school to get my education in all this). So I am thinking of changing the rear differential on my 1997 GMC c1500 from a non limited-slip to a positrack. First of all, is this something that I could do with instructions, or would this best be done by a shop? Ill probably go down to a local scrapyard and see if they have anything in good shape. If that fails, where should I look to get a new one? Thanks :)

TD94
Click to expand...

First, welcome aboard! I think you are on the right track with a complete axle from a wreckin' yard. however, you will only find rear locking differentials. These aren't really lockers as they lock and unlock depending on wheel speed, but replacing the complete axle is 10x easier than pulling the gears and carrier, installing the locker and setting up the gears. On the other hand, if this is going to be your chosen profession you can't buy experience. My brother-in-law is purty good mechanically, but his profession is real estate. He bought a new Viper and didn't like how it accelerated. He bought a book, a set of gears and installed everything in the Viper out in his driveway. So I know it can be done.

Some extra help. If your wreckin' yard doesn't pull the axles out of the truck the way to know it's the right axle is to check the RPO codes on the glove box door. Here are some of the gear ratio codes that will be located on the glove box door to help you decide what gears you have and want and the locking rear diff:

G80 : Rear Locking Differential

GS1 : AXLE REAR, 2.73 RATIO
GS3 : AXLE REAR, 3.73 RATIO
GS4 : AXLE REAR, 3.70 RATIO
GS5 : AXLE REAR, 4.11 RATIO
GS6 : AXLE REAR, 4.56 RATIO
GT1 : AXLE REAR, 2.56 RATIO
GT2 : AXLE REAR, 2.29 RATIO
GT4 : AXLE REAR, 3.73 RATIO (DUP WITH 5 X 1)
GT5 : AXLE REAR, 4.10 RATIO (DUP WITH GT8)
GT7 : AXLE REAR, 3.33 RATIO
GT8 : AXLE REAR, 4.10 RATIO (DUP WITH GT5)

and more

GU1 : AXLE REAR, 2.41 RATIO
GU2 : AXLE REAR, 2.73 RATIO
GU4 : AXLE REAR, 3.08 RATIO
GU5 : AXLE REAR, 3.23 RATIO
GU6 : AXLE REAR, 3.42 RATIO
GV1 : AXLE REAR, 2.73 RATIO
GV2 : AXLE REAR, 5.83 RATIO
GV3 : AXLE REAR, 3.08 RATIO
GV4 : AXLE REAR, 3.36 RATIO
GV5 : AXLE REAR, 3.55 RATIO
GV7 : AXLE REAR, 4.11 RATIO
GV8 : AXLE REAR, 2.72 RATIO
GW2 : AXLE REAR, 2.56 RATIO
GW3 : AXLE REAR, 2.56 RATIO
GW4 : AXLE REAR, 3.31 RATIO

Good luck!! :thumbsup:
 
Cool, thanks for the info. I would actually prefer to modify the current differential since I dont have the equipment to remove the axle (not to mention my dad would not be terribly happy). Would be nice to have in the snow here though :) I would prefer a limited slip to a locker though. I have no experiance with this though, but if this is something I could do in my garage, I might be interested. Where would you recommend a kit from? Would there be somebody (or a book or the like) that could walk me through the procedure? Thanks :)
 
On that note, I shoulde ask is it actually possible to just change the differential or would I have to change the whole axle?
 
yes you can change just the differential as was said earlier it's easier to change the whole axle but if you want a specific posi it can be done
 
TruckDude94 said:
Cool, thanks for the info. I would actually prefer to modify the current differential since I dont have the equipment to remove the axle (not to mention my dad would not be terribly happy). Would be nice to have in the snow here though :) I would prefer a limited slip to a locker though. I have no experiance with this though, but if this is something I could do in my garage, I might be interested. Where would you recommend a kit from? Would there be somebody (or a book or the like) that could walk me through the procedure? Thanks :)
Click to expand...

TruckDude94 said:
On that note, I shoulde ask is it actually possible to just change the differential or would I have to change the whole axle?
Click to expand...
In order to install a limited slip you would have to pull the rear cover, axles, and carrier.

Don't let the Rear Locking Differential label confuse you, this is GM's "limited slip" unit although it really isn't in the truest sense. And, changing the whole axle only requires ratchet, sockets some combo wrenches and a floor jack. Really easy it's just heavy.

Replacing the carrier in the differential is not for the faint of heart but it can be done. I would look at Eaton for a limited slip unit and they probably have a kit. I would google for a book or video that would guide you through this, or about 600 bucks to have it done.

Real lockers are like Detroit Locker, and Grizzly Lockers just to name a couple.
 
http://www.summitracing.com/parts/ETN-19554-010/?rtype=1

Cant remember what bolt configuration mine is (Im on vacation at the moment), but when I return Ill have to take a look. They have a few different bolt configs on summit, just as an example I pulled up this one. I popped up the instructions and after looking at that I might just have a shop do it for several reasons. For one I would need go get a crapload more tools for this, and the truck is a daily driver so I would need as little down time as possible, and third I can say I had it professionaly done when I sell the truck. I appreciate all of the feedback, and this will come in handy in the future when if and when I wind up getting me a project car :D Doesnt sound like too bad of an install but I just dont want to try it for the first time on my daily driver in case something goes wrong :agreed:
 
That would be if I got just the differential though there, if I find an axle at one of the local scrap yards, Ill give it a shot myself :)
 
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