i want to change the differential on my 89 transam 305 tbi but i'm not sure which axle spline i have. i heard that you can find out by the vin number, which number would that be? btw, i'm getting slp posi. i also heard that you need an install kit? where would i get that?

 

For questions like this use the "Transmissions and Drivetrain" board.

If your rear end is stock, it'll have the 28 spline axles. '88 (supposedly) is the last year of the 26 spline axles, but with GM it's hard to say that's a definate. There are probably a few '88s that have the 28 splines, but regardless, your car will have the 28 spline for sure.

I wouldn't recommend you change the rear yourself unless you have the proper tools. It's a lengthy, precise process. One wrong adjustment and your car will be sitting on the side of the road after a few hundred miles.

I'm not saying you "can't" do it yourself, but the rear end is a VERY sensative area. I know I'd never do my own unless I had specific training in that area.

 

i wasn't intending on even touching the rear end i just wanted to find out whether i need to replace the axles, thanks

 

If you have an '89 with drum brakes and a 10 bolt, you most likely have the 26 splined axles.

 

If the carrier that your getting is a series 3 carrier than you will need 28spline axles. Series 2 carrier is 26spline.

Dyno Don is right also. If you have drums than you have 26spline axles.

 

That is so wrong on both accounts.

A 2 series or 3 series has to do with the mounting flange for the ring gear. Anything that is 3.08 gear or lower (numerically) is a 2 series carrier. Anything 3.23 or higher is a 3 series. It has nothing to do with the spline count on the axles.

And whether the car has drums or discs also has nothing to do with it. I had a 1990 V6 Camaro with rear drums that had 28 spline axles. I have a '92 Camaro RS with rear drums that has 28 spline axles. My friend (4mula88) has an '88 Formula that has 26 spline axles.

 

more than likely you have 26, i have yet to see someone on the boards with a 89 or older thirdgen with 28 spline axles.

 

didn't they switch from 26 to 28 halfway through 89, i have heard of people with 89s that have both 26 and 28 spline axels, you almost have to pull an axle out and count the splines to know for sure.

 

I'm sorry I wasnt specific enough. I meant on 89's and some 90's you can assume that you have 26spline with drums.

Quote:

A 2 series or 3 series has to do with the mounting flange for the ring gear. Anything that is 3.08 gear or lower (numerically) is a 2 series carrier. Anything 3.23 or higher is a 3 series. It has nothing to do with the spline count on the axles.

I was assuming also that if he was going to a LSD that he would be changing gears also.

Quote:

And whether the car has drums or discs also has nothing to do with it. I had a 1990 V6 Camaro with rear drums that had 28 spline axles. I have a '92 Camaro RS with rear drums that has 28 spline axles. My friend (4mula88) has an '88 Formula that has 26 spline axles.

Once again, they changed axles in mid year sometime. I didn't say that all years with drums have 26spline.

Ok, you won. Now are you happy.

 

youll be lucky if your 89 has 26 splines. I have a 90 RS with rear drums and i have stock 28.

 

I have never seen or heard of a 305 TBI car from 89 having 28 spline axles because GM didn't make them for that type of car in 89. So I am 100% sure you have 26 splines.

If you were thinking about going with the SLP take-off posi and you can't now because you have a 26 spline then Auburn and Eaton both make differentials for 26 spline rear ends. Good luck.

 

or you could swap the axles and get the SLP posi, might be cheaper than buying the auburn or eaton posi.s

 

They have 3.23 gears that are 2 series, Richmond gears make them, that's what I have in my rear.

 

richmond makes all sorts of gears, you can get 4.11s that are 2 series if you wanted.

 

or just go to a junt yare and get the 28 spline from a 90-92 car
there are 3 91/92 v-6 cars in my local junk yard all with the ground effects allready gone damm.
Ryan

 

which would be better to do, get a new axle and differential or just get a 2 series differential? I don't want something crapping out on me, i heard that the 3 series is better or the 28 spline is better or something like that, so which is the better thing to do? Where would I get good gears 3.73? Also I heard that Richmond gears "whine" what does that mean? I don't wanna get something that adds some noise like that. So which are the better 3.73s out there, and which differential shoud i get with them, as well as an axle?

 

I use to have 3:73's from Richmond that were carrier 2's for my open differential.

 

The drum 3.42 rear from an 89 v6 Firebird I pulled from a junkyard had 28 spine axles but I think most came with 26 spline. I guess I just got lucky.