3rdGenHitman

ok with my 89 i have heard i can get the rear end out of a 4wd s10 blazer and it would have something like a 3.73 posi in it. how true is this? also, what years would i be looking for, what size, etc.
then if i did put that rear end in, what else would i have to change? would it be the same driveshaft with different u-joints, or what? thanks in advance.

Marc 85Z28

iTrader: (3)

The complete rear axle will not work. The ring&pinion can be swapped, along with the carrier if the spline count is correct. Some S10s did come with 3.73 gears and limited slip differentials, but those differentials are garbage.

3rdGenHitman

so with mine being a 2.73, can i just get the ring and pinion gear out of a 7.5 from an s10? also is there a kit thats sold aftermarket for this? sorry probably newbie quistions, but im a newbie to rear ends.

big gear head

No, you can not put a GM 3.73 gear on a differential that had a 2.73 gear on it. The 2.73 uses a 2 series differential and the 3.73 fits a 3 series differential.

The limited slip differential that is used in the S10 is a Eaton Governor Lock. It is no good for performance use. It will break.

Your car probably has 26 spline axles in it. In '90 the 7.5 rear end was upgraded to 28 spline axles. You will have to use a 26 spline differential or upgrade your axles to 28 spline from a '90 to '92 Camaro or Firebird.

The S10 rear end will not fit your car and only Camaro and Firebird rear ends will fit.

3rdGenHitman

Ok I see. So what would be the best bet for getting something like a 3.73 ratio position in? Do they sell options for it, or is there another way?

3rdGenHitman

ok update here. i counted the gears by turning the tires the other day n it counted around 2 and 3/4 turns per one turn of the driveshaft. so it should be a 2.73. well i roasted the tires and it is a posi all day. how is that possible?

AlkyIROC

Providing the diff in your car is still original, an RPO code can tell you what gear ratio is in the diff. The TGO database can also pinpoint exactly which gears were originally in the car based on year, model, engine and transmission that was originally in the car.

According to the tech data, 3 different cars came with 2.73 gears in 1989. An RS with a V8 and auto trans and 2 different 305 IROC's. A 350 IROC with a 9 bolt diff came with 2.77 gears

A 1989 RS never came with a 350.

It's not hard to spin tires if traction is poor. Worn/old tires etc. Being able to spin the tires just tells me you don't have enough traction to get the vehicle moving properly unless you're off dry, clean pavement.

big gear head

If you have a 2.73 posi rear end and you want to keep the posi you can get a special thick aftermarket 3.73 gear that will fit the 2 series differential.

3rdGenHitman

well talking to some other 3rdgeners i found out that the gu2, which is what i have, came with a posi option. so it is a posi. so today i managed to fix the fuel pressure problem, tv cable issue, and found out it has a manual valve body and posi. mission accomplished.

big gear head

If it is a posi then you will have a G80 code to go along with the GU2 code. No G80, no posi.