How hard are they to change and can it be done on the car? I never really messed with a trans before but my speedo is way off and the calibration box doesn't seem to work with the digi. dash.

 

The driven gear is a piece of cake: undo the cable and one 10mm bolt.

The drive gear is a bit more involved. You have to remove the exhaust hanger there at the cat, open the torque arm bushing clamshell, and remove the driveshaft so that you can remove the tailshaft housing. Then the drive gear is exposed and you can remove the metal clip and slide it off the output shaft to replace.

 

Speedo gear swap

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'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
3.73 Posi
4wheel Disc Brakes
Summit 1-5/8" headers, 2.5" Dynomax catback.

Best 1/8: 9.519@72.74

'97 Bonneville SSE