I have a TH400 with the GM electric speedo sensor and reluctor wheel. After changing the tooth count in my tune from 17 to 40 the speedometer is of by 70mph while I'm driving at an actual speed of 50 verified by my GPS. I'm about to bump up the tooth count in the tune unless someone can tell me whats going wrong. Did GM make another reluctor wheel for the Th400 with more teeth? I never counted the teeth on mine to verify. Anyway, hoping someone may know whats going on.


Hummer

 

OK, got it figured out. Not only do you have to change the reluctor tooth count (VSS pulses rev-trans) you also have to change the VSS pulses per mile. In my case going from a 6 speed 17 tooth wheel I had do devide 40 by 17 and came up with 2.35, then take that number and multiply it by the current VSS pulses per mile and thats your final VSS pulses per mile number.

I found this thread from about 3 years ago that explained it, had to read it a couple of times before I understood it. Just hope it helps someone in my situation out in the future.
https://ls1tech.com/forums/automatic...ners-info.html