Hmmmm, do I have 3.42 gears?
 

I've noticed that the rear in my 96 SS seems awfully rusty compared to everything else on my car. So noticed that on the highway in overdrive, I'm pulling 2200 rpm's at 70 mph. So if you work it backwards with the 275/40/17 tires it looks like it works out to 3.42 gears instead of 3.23 gears. Obviously it depends on the accuracy of the factory tach as well. But does anybody know if there is a date casting or any code stampings on the 4th gen rear so I can check to see if it was swapped out at some time?

If Im not mistaken the Auto SS's were available with the 3.42 gear ratio as part of the SS package, but I could be wrong. Sorry i dont know of the stamp numbers.

Really? I've never paid attention to the SS cars because I figured I would never own one. The sticker on the door shows the 3.23 gear option but I have no idea if the SS would override that with 3.42's or not.

To my knowledge, there were no A4 SS's with 3.42 gears. They would have the 3.23's.

Remember, the factory tachs read 100-200RPM higher than actual engine RPM. With 3.23's you would be around 2,066RPM. and the tach error would account for the difference.

The code for the rear axle ratio is on the RPO sticker... should be GU5.

GU5 = 3.23
GU6 = 3.42 :)

Yeah, I need to hook up a scanner to verify the tach rpm's. But at idle my car tachs at 700-750 rpm's in park so it doesn't seem to be reading high at that point. The LT1 in my 68 Camaro would idle around 575-600 rpm's and is sounded like it had a cam in it because it was so low. I'll take a look at the rear. I just can't believe how rusted it is compared to the rest of the car so it wouldn't surprise me if it's from a different vehicle.

i know auto ls1's are set to idle at 550 when warm i would assume lt1's are set around there...so lets say its set to 650 stock that would mean your 50-100 rpms off at idle.

pull the cover, might as well change the fluid anyway, and see what the gears are. wouldnt hurt

put the car up on jack stands.

put a mark on the tire at a point, go underneath the car, spin the driveshaft and count how many rotations it makes before the tire is back in the same position.

thats an easier way to find out in my opinion rather than taking the rear cover off.

It definitely has 3.23's, I just jacked it up and counted the turns. It does look like the original rear with no signs of the rear cover ever being off and none of the nuts/bolts look like they were ever removed other than the torque arm. I know it looks like the trans was removed at some point in time so that could be why the torque arm was removed.

Stock LT1 A4 programming is 550rpm in gear and 650rpm in neutral, as long as the coolant temp is 176degF or above.

The rears rust like crazy... normal.