purestreet92

I just bought a 92 rs a few days ago and have a question about the correct rear axle gear ratios.From what ive read and info ive found all 305 rs came with 2:73s in an auto car and 3:08s in a 5speed...mine is a auto but it has from what ive came up with using rpm and gearing calculators and based on my rpms vs mph in driving at speed would be 3:42s.....the car is an all orginal stock car and in great shape so i dont think anyone would have changed them to lower gears.it was serviced at the local gm dealership where it was bought new its whole life.i got it from the orginal owner.i have all the service records from everything thats been repalced or done to it.also it did have the trans repalced with a new gm trans about 20,000 miles ago.if someone did have the gears changed they would have also had to changed the speedo gears in the trans.the speedo reads correctly ive checked it with a hand held gps....any ideas?do any other ppl on here have a 305 rs with 3:42s from the factory?

green92

Its hard to say on the exact numbers. But i wanted to know the same thing on my car when i first got it. DO NOT trust the the haynes manuals, by what info i got from them compared to what id numbers were actually on my rear end they didnt match. You are right so far and yes they did have some with the 342 rears a friend of mine had a 91 rs auto that had the 342 rear in it. Just go by rpo codes and have your local dealer run your vin thats how i actually confirmed mine. Hope this helps. By the way i have a 92 rs 305 5 speed with a 308 rear.

JamesC

iTrader: (5)

Or eliminate the guesswork. Jerk the diff cover and look--fluid probably needs a change anyway. Numbers are stamped on the ring and pinion:

41 : 15 = 2.73
41 : 14 = 2.93
40 : 13 = 3.08
42 : 13 = 3.23
41 : 12 = 3.42
41 : 11 = 3.73

JamesC

purestreet92

Thanks for the info guys....i didnt think these cars came with 3:42s.wonder what made them put these gears in certain cars?does anyone know if it was an option or was it something the factory did when they ran out of the correct gear sets and just threw them in to keep production going?...yeah im going to pull the diff cover off soon as the weather warms up a little and change the fluid.thanks for the gear ratio chart JamesC that will be very helpful.

pontiacguy1

Someone could have swapped out the rear end at some point... The V6 5 speed cars came with a 3.42 geared open differential. Someone could have gotten that rear end and the speedo gear out of the same car, and done the swap.

krisb410

iTrader: (9)

There is your error right there, the 92 tachs are known to read incorrectly!!

Check out this thread:

https://www.thirdgen.org/forums/elec...light=fix+tach

purestreet92

Yeah i thought it could be a v6 5 speed rear axle but like i said the car was a one owner car and always serviced at the local gm dealership.i cant see why they would throw a set of lower gears in it and nothing else and the fact it was a woman that owned it and didnt seem very performance oriented about it....as for the tach it actually seems to read pretty right on about the rpms...a friend of mine has one just like mine of the same year with 2:73s.going down the road at the same speeds there is a noticable diffrence in the rpms just based on the sound of the engine.that and his has full exhaust and intake and mine is stock as the day it left the factory and it will pull about two maybe three cars on his from a roll race or a dig....we figured that would be a good way to see if it was a diffrence in performance. i dont plan on modding it at all.im gonna try to keep it stock and orginal as possible.

krisb410

iTrader: (9)

Like James C stated earlier in the post, only way to know for sure is to pop the differential cover off and look inside.

Using the factory tach, and "pacing/racing" a friends car is not an accurate way to find out what rear gears you have.

IIRC: RSs with the LO3 305 TBI engine and auto trans was only available from the factory with 2.73s. So if your so diehard about this being a "same as left the factory" car, then you have 2.73s.

Here is a breakdown of what was available on the RS models from the factory, no optional gears were available.
LHO(v6)/auto= 3.23
LHO/man= 3.42
LO3(v8)/auto= 2.73
LO3/man= 3.08

Sonymaster20

iTrader: (3)

I also wondered about this but have gotten some good info from this thread. One question I have is, are these all one wheel peelers? Or do they have some sort of posi/dual spinning wheels when doing a burn out. I don't dog my car as I'm 16 but Just would like to know. I have the 305 Tbi 5 speed.

green92

Not sure on the rs models for 91 and 92 i know z28's did have posi. I actually had a 323 rear from a 85 v6 car that was posi. I ran it in my car till it finally gave up and the spider gears exploded. Then i had to go back to my open wheel 308.

JamesC

iTrader: (5)

Anything might have happened to the rear since the car was new. Drop the cover and take a peek for the sake of certainty. The Auburn limited slip should look like the one in the following pic:

https://www.thirdgen.org/forums/atta...s-dsc00148.jpg

JamesC