I recently purchased a rearend from one of the local junk yards based mostly on the fact that it's rear disc, and I've been wanting to put rear disc on my car, and that there's a fair possibility that it has limited slip and a 3.23 gear ratio.

that's a really bad explaination of how it went, but over a week and a half, thats basically how it worked out.

I bought the whole rear assembly minus calipers and pads for 160, so it's not a terrible loss no matter what it has.

the problem was that the car was on the ground, so I couldn't see the differential housing itself, I couldn't check the codes, I couldn't really do anything.

like I said, kinda on a whim.

what I'd like to know is what did I most likely buy?

I got the rearend out of a '91 GTA Trans Am with a 305(I checked the vin), I'm not positive, but I BELIEVE that I saw both the G80 and G92 rpo codes, but I'd looked at a lot of maro's/birds that day, and some had it in the console and some didn't.

from what research I've managed, I know that the GTA's with that setup all came with either 3.08, 3.23, or 3.27 ratio's, and obviously when I see it tomorrow I'll be able to knock out at least one by counting the bolts. I also know that all Iroc's/z28's from 90 on came standard with limited slip, but I don't know if GTA/trans am worked similarly or not.

so, what do you guys think is most likely?

a rear disc 91 305 GTA Trans Am, what ratio did I get, and did I get a limited slip differential?

I'm happy no matter what, but it'd be nice to know just how "good" of a deal I got.

thanks.

 

Well i dont think it would be the 3.27 since they were offered in the 9 bolt and its always been my understanding that you couldnt get the 9 bolt in 91-92 cars.If i had to guess i would say 3.23 10 bolt rear on a GTA.IF it was the original rear on that car then theres no doubt it has posi.

 

from what I've read the 3.27 was still a possibility on the '91, that of course only being in the 9-bolt, but in either case I hope you're right, I really do.

I'd assumed that since it was a top of the line option package it would have the "best" rear end, that in my opinion being the 3.23+ posi, but I don't know if they went a different route with the 305 or not.

I hope not, heh.

thanks.

 

You got it from a yard so it is safe to say that you will need to at least change the fluid. So, count the bolts on the cover to determine what rear it is. Then pull the cover and look inside. Either count the teeth or look for the teeth ratio stamped on the gears. You will have your answer in about 2 minutes. There is no way to tell what gears a 15 year old car has without taking the cover off. RPO's only tell you what the car came with stock and not what camaro joe swapped into it back in '94.

 

Did you get an LSD? Well, support the axle and try turning one of the hubs. If the other hub turns in the same direction, then it's LSD. On a non-LSD the other hub will turn in the opposite direction.

Mark.

 

so, I got the rearend today.

ya....

it's a friggin bw 9-bolt 3.27 lsd!

160 bucks, I got that, the trailing arms, the sway bar, the springs, as well as pieces of various other parts, heh.

oh ya, two quick questions.

1: are the trailing arms stronger on trans ams, and are the springs stiffer? i know either the front or rear springs were stiffer, but i'm not sure which.

2. the caliper brackets are opposed on either side, the left side facing back, the right side facing front, is this normal?

 

The control arms/trailing arms are the same. I wouldn't use the springs. They are old and can be assumed to be no good. If you don't want to go aftermarket you can buy moog replacement springs for your car.

 

Perfectly normal.

 

I've always been told that springs don't actually go "bad", but I don't have money to replace the springs either way, so that's out of the question.

the springs are also off of a 91, compared to my factory 88 springs...wear and tear in that case wouldn't seem as much a problem...I dunno, I'd like to know if they're stiffer or not.

 

awesome.

now just to put calipers on it.

oh ya, and put it on my car.

 

Springs do compress over time, hence when people replace their spring with say a one inch chop, their car still sits higher. The one inch chop was based on new spring length!

Mark.

 

interesting, never heard anyone say anything like that before...

what is the stock ride height? I'd like to see if I'm lower than I should be.

 

You have been told wrong. Springs wear just like any other movable part. The material weakens over time due to the constant tensile and compression forces it experiences during normal operation. The natural movement of the spring fatigues the material. Thus they lose their spring force. The spring then eventually becomes inadequate for what its design intent was. This can be dangerous. The same principal applies to valve springs.

 

there are 40+ year old cars out there running on the original springs and valve springs.

I understand that there's wear and tear, and they obviously won't always work up to spec, but I've never seen a non-wrecked car just have a spring completely collapse one day...

 

There's a difference between "going bad" and "complete failure". Every one of those 40+ year old cars out there could benefit from new springs.

 

I am not talking about a complete collapse where the spring breaks. I am talking about fatigue. Do your running shoes fall apart one day when they are worn out? No. They just don't dampen the loads you impose on them the way they did when they were new. You therefore hurt your knees, ect ect.

Old springs loose their spring rate. That spring rate is crutial to the dynamic balance of the system they are used in. Worn springs will cause your car to float and it could be dangerous. You will under dampen your suspension and your car will feel like a buick land yacht.

Have you ever heard of valve float? Why do you think you must match your valve springs to the cam you choose?

 

alright alright alright fine, I won't use the springs, sheesh.

 

LOL