From a M6 to 4L80 speedometer problem

[RandyWS6]

I just install a 4l80 in my 2000 TransAm-M6, The car has a 4:30 gear and 335/35/17" tires. And that was with the M6 also. Can some one help me program my speedometer.While driving at 35mph the speedometer reads 80mph. I also have cos-5 if that matters.

[Tre-Cool]

u need to change the soeedo cal area to a 40vss pickup from 17. i had to do the same when going to a t400.

or running the built in calculator would be better

[RandyWS6]

O.K. thanks.

[RandyWS6]

That fixed it, thanks alot.