What gears do i have? I think its the 2.77s. I know they came with 2.77s 3.27's and 3.45's?? I went to 9bolt.com to order some gears but Miles told me that if i have the 2.77 gears the 3.73 gears will not fit, why is that? Does anyone know how i can accuritly tell what gears i have? I really need gears for my car because the 4l60e transmission is computer controled and i have to have the computer calibrated to what gears i have in the rear so the tranny will shift at the right rpms. Thanks for the help.

Bobby

 

If the rear-end is original, check the rpo codes in your center console. It's either 2.77's or 3.27's. The only way it has 3.45 gears is if the car was originally a G92 manual transmission car.

 

make a mark on your driveshaft.

with the car in the air, turn the wheel untill the driveshaft makes 1 full revolution, taking note of how many turns of the wheel it took to accomplish that.

3 and a half turns would indicate a 3.45 ratio, two and 3/4 would idicate 2.77, and so on.

 

Pull the cover and check the stamped ratio on the ring gear, the only positive way to verifly the gear ratio. However; it sounds like you have the 2:77 ratio with a 2 series carrier. But you say the tranny is 4160E?? No 9-bolt came stock with that tranny.
Pull the cover.

 

the car is an 89, i installed the 4l60e with the lt1 instead of using my worn out 700r4. Thanks for the help guys.

 

Don't forget they made a 3.08 9bolt I have 1 now from 86 trans-am 3.08 locker disc reared $150 plus shipping thanks john

 

Bob,

If your RPO label isn't clear, you should be able to find a Borg tag on the right axle tube, with data including the installed gearing. Chancecs are, you have a 2.77 sincec they were more abundant. If you need a resource, check: http://www.9bolt.com/

 

look for ID tags on the rear end. I just sold a 9bolt with Factory 3.70's

If no ID tags are on it. do the drive shaft spin trick or pull the cover off the rear end.

 

I had the same problem. There should be a tag on the rear which is attached to one of the cover bolts that will tell you what gears are in there. As far as the 9bolt.com he is too much money plus you can't change the gears from a 2.77 to a 3.23 or 3.45 beacuse the casing is different and the 3 series gears are different. If you do have the 2.77 or 2.73 gears you will have to buy a diffferent rear if you want to go to the 3 series. If you have drum brakes you will have no problem finding a rear at a junk yard but if you have disc brakes it will be a little harder to find but i just went through the same thing and ended up finding a 3.27 disc brake rear at a swap meet for $100.00. Be careful the braking system is different from the years 82-88 the 89-92. If you get the wrong brake setup it's no big deal all you have to do is change the backing plates. Good Luck. Hope i helped a little