1992 RS, 305 TBI, Auto originally 2.73 rear.
Swapped to a 3.73, Running Iroc 16s. Can someone tell me which driven and drive gears I need to correct the speedometer? Also, I installed a rear end from what I was told was a 2002 trans am, and I used a Richmond overhaul kit when I rebuilt the rear. The front pinion seal is puking. Did they change pinion or yoke diameter throughout the years? It's leaking between the seal and the outside of the yoke.
Thanks in advance!

 

What size are the rear tires?

Example: P245/ 50ZR16 = 245-50-16 = 245mm width, 50% sidewall aspect ratio, 16" diameter wheel.

Post your tire size in the equivalent form of: 245-50-16

The tire height is part of the equation, with the ring and pinion ratio for the speedometer gears.

 

You need a 15 tooth drive gear (gray) and a 43 tooth driven gear (purple) for a 3.73 rear gear ratio with 26-inch tires.

A 245/50-16 is 25.6 inches, so a 44 tooth (dark gray) driven gear is what you'd need...

 

I'n interested in this also, what does everyone use to figure out what color and tooth count you need

 

For the 4L60, 15/44.is what is available.

 

I am running the 245 - 50 - 16 so that is a 25.6 inch tire. I still have the 700r4 trans. Originally the car had 2.73 rear and the stock 15in color matched wheels. Can anyone tell me if either the drive or driven gear will be reusable and if I will have to change the housing for the driven gear? I read this note on TCIs website:

"Two 2.078" diameter housings, each made from either aluminum or plastic, are available for driven gears with 34 or more teeth. One fits gears from 34 - 39 teeth and the second one fits gears from 40 - 45 teeth."

Thanks again fellas

 

My 90 Formula originally came with 2.73 rear gear. I had a red, 17-tooth drive gear from the factory. I swapped out to a 3.42 gear and was able to swap out the original driven gear for a 45-tooth, but first had to switch to the other VSS, as you mention. You might read up on the sticky: https://www.thirdgen.org/forums/tran...eedometer.html

 

Jack the car up, remove the 10mm headed M6 bolt, use a mirror to check drive gear color and count driven gear teeth. Going by color isn't a reliable way to count teeth. But it's very likely a 2.73 car still has a red 17 tooth drive gear.

If the car functioned correctly before gear change:
buy a 44t driven gear, 15t drive gear, and if it was a 34-39t driven gear, buy a correct 40-45 VSS..