I had an m6 tune, and swapped to a th400 trans with the gm 40tooth wheel and sensor assembly..

I searched for a while and found some dta on the calibration for the seedometer to work but nothing concrete and i still feel that my speedo is off

with a 26" tire and 3.73's in the rear, stock geared th400 i was at about 6300rpms@110mph, i would have thought i would have been at around 130mph turning that rpm

its a 98 so its different than other years with the tire/gear configuration
current tire/gear =6.99

general vss pulses per
mile= 115378
rev-trans= 40.0000

final drive ratio
trans revolutions/mile= 839.7070

thanks

 

I show you should be this:
6.971 T/G
115733.95 VSS Pulse Per Mile
2893.35 Trans revs/mile
775.7 Tire rev/mile

 

ok, I'll try that out this weekend when the weather clears up