my rear diff gears have a lot of play and I want to replace them.
I want to find out the stock gear ratio. is there a way to find this information .
97 z28 lt1. automatic trans.

 

If you have the cover off, jack the rear up and put the car in neautral, and spin the carrier until find the stamped numbers on the ring gear. Divide the two to get the ratio. Alternatively, check the glove box for the RPO codes for the ratio.

 

or jack up the rear, both wheels. if you have posi turn one wheel one full rotation and count the times the driveshaft turns. if it turns 3 and 1/4 turns you have 323 gears, if it turns 2 and 3/4 turns you have 273. you have posi if when you turn one wheel both wheels will turn the same direction.

 

gu2 2.73 gu4 3.08. gu5 3.23 gu6 3.42 , my 95 i got gu2 i think thats the real reason i want 3.42 gears with all the tlbs i got now

 

Thanks for the information.
I have the GU5 3.23 gears.
if I change to 3.42 what should I expect to change .
better low end performance? how much top end will I lose?
my mechanic friend recommends 4.11 , is that too much if this is my daily driver.
I want better performance , but am not going to the drag strip.

 

4.11s are a little much for a A4 that isn't going to see drag time. 3.73s is the lowest I'd go with an A4 that was doing street duty.

You probably won't notice much change from 3.23 to 3.42. But you will be slightly quicker from a dead stop and as far as top end goes, you won't lose enough to even care.

 

You still want to check physically to know for sure what gears you have. A lot of things can change over the years, unless you've owned the car since new.
An RPO code only tells what GM put in your car, and is totally worthless if a previous owner replaced it with something different.

 

yes with mine.it was all stock ,but feel like 3.23 ,sometimes