I recently replaced the original 2.73 rear axle on my 91 Camaro RS for a 3.42 rear axle and, of course, my speedometer is way off. I just ordered a replacement driven gear (from 37 tooth to 45 toth) and a speed sensor to match it. I have never replaced any of the above before and would welcome any tips as to how to do either one... I imagine the speed sensor should be fairly simple but not sure about the driven gear itself.

 

The speed sensors just screws into the tail shaft of the tranny... the driven gear just fits in behind it. You might get some fluid out when you change it but otherwise its a really simple job.