I have stock gears in my 88 trans am right now.What are stock gears for this car its a 305 tpi auto.And is it posi? I also want to put in some 3.73 gears where would be a good place to get these with posi.

 

You can find the available stock gear ratios in the tech data on this site. Good used 3.73's and 4.10's are common stock gears in S10's and Somona's and Fbody's. So are "3series" posi diffs. If yu get one from a '90 or newer with 28 spline axles, get a set of 28 spline axles for a 90 or newer 3rd gen fbody too. Your's are 26 spline. Save the pinion shim from your present pinion
gear. 99% of the time that's the right shim for your new gearset in your housing.

 

Stock gears are probably 2.73 or 3.23. It ought to be a posi. You should be able to check the RPO codes and see what it came with stock. Or you can jack up the rearend and see for yourself, which is probably a better idea, just in case something was swapped out or the posi ruined. Turn the driver side wheel foreward and watch the passenger wheel. If it goes foreward also then you have a posi. If it goes backward then you don't. You can check the gear ratio by counting the number of times the driveshaft goes around for every one revolution of the wheel.

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91 Z28
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