Hi all. I recently bought a 90 cummins 350 dually with the 3 speed auto. It has the 3.07 gears in the rear. I couldn't stand driving the auto especially with no overdrive, so I put in a getrag 360. I got all the parts from a guy that works on these machines a lot, and the conversion was pretty simple. However, my speedometer and odometer is way off now and tends to only work occassionally. I put a new speed sensor on, but no luck. I used the sending unit off of the 727, because the plug was different on the 360 that I got. Does anyone know if I have to get my pcm flashed or anything. Or do I need to find another sending unit? Thanks for all your help.

 

think the 90's use a gear and sensor off the xfer case don't they?

I would be sure that sensor is good and the wiring to it is good.

as for correcting the speed reading, think you had to actually change the gear on the sensor to correct for different ratios...

vehicle PCM's back then were very primitive. didn't even have OBD-II