I recently swapped my 87 camaro rear end for one from a 90 Z28 w/ posi and disc brakes. The old one had 2.73 gears and the new one has 3.23. I am looking for the speedo gear to coinside with the new rear end. I have the red one now and i think i new the light blue one with a couple more teeth, I believe it is 45 teeth.

 

What did you do, 3.23/2.73x37=44? doesn't work that way. If you are running 225/60R15, 245/50R16, 245/45R17 or 275/40R17 tires, you can use either a gray, 15 tooth drive gear, GM pn 8642620, witha blue, 38 tooth driven gear, 1359272 for cable-only speedo or 25513045 for the other style, depending on which dash you have, or ared 17 tooth drive gear, 8640517, with purple 43 tooth driven gear, 1362196 or 25513050. If you're running a 255/50R16, or a 235/60R15, or a 255/45R17, then use the blue 18 tooth drive with the light blue 45 tooth driven, 9775187 or 25513052. If you're running a 245/60R15, 295/50R15, 225/60R16 or 275/40R18 then use the 18 tooth drive with the dark gray 44 tooth driven, 9780470 or 25513051.

 

You lost me. Sorry. I don't know what my drive gear is but I have the purple 43 driven gear now. It was working fine before I swapped the rearend with the 2.73 gears. When I bought my new wheels I used a tire calculator from Discount Tire's website to calculate the tire size I needed to keep my speedo correct. I went with a 285/35R17 and everything turned out well. Now I have 3.23 gears in the rearend. Chevy has discontinued the driven gear.

 

This may help.