This thread? http://forums.amceaglenest.com/index.php?topic=25422.0
How big is the difference in speedometer function between OBDI and OBDII?
To be honest I haven't a clue, I think there is alot more wiring and another computer just for the trans. I know that my 98 bravada (OBD 2) has like 5 computers in it total and I hate it with a passion
For instance, GM speedometer cables turned 1000 revolutions every mile. When GM went to gear driven VSS, the sensor turned 1000 revs/mile, but made two pulses per rev and put out 2000 pulses per mile.
For a bunch of later hardware, GM switched to a magnetic reluctor and has used counts from 14000 to 24000 pulses per mile.
I was wondering if you knew that sort of info.
Finally, on the newest ('04+) cars, the instrument panel gets all its info from the data bus and there is no direct wiring for any of the instruments.
Obviously the thread I linked is an '89 Cherokee which still used the speedometer cable.
Really, I was just curious to see if the signal info was out there. Fundamentally, it doesn't *really* matter what kind of signal the speedometer likes, as I will be able to tune the pulse count that the ECM generates to drive the speedo.