Are the transfer gears the original? If they were changed to a different ratio that could be your problem. Very easy fix too assuming you can find the correct ratio.

https://dodgeforum.com/forum/dodge-c...smissions.html

 

They should be the same. The reman tranny was from a 2004 T&C 3.8 installed in my 2003 T&C 3.8. I wonder if replacing the instrument cluster is a potential fix in that I had to jump start the battery the last drive before taking to the tranny shop for repair. I read earlier that jumping the battery can cause your speedo to get out of calibration. I ran this by the dealer who said no way jumping would cause this problem. Any thoughts on this? Thanks.

 

I would verify the gears are the same.

 

Pull the speed sensor already. If you put the axles back in the trans with the speed sensor attached you could have broken some of the teeth off of the sensor. Replacing the sensor outright seems like a reasonable choice right now. Also make sure you didn't pinch a sensor wire in the bell housing or otherwise.

 

The speed sensor isn't anywhere near the axles.

 

Is the sensor not a helical gear riding against the passenger-side axle? I know of the input and output Hall effect sensors but I recall there being a mechanically-driven one as well. I may be very confused...

 

Maybe on the older ones. This year would use the output speed sensor which reads before the transfer gears and the diff which is why I suggested the transfer gears. I have a Neon that I changed transfer gears in to give it more of a highway gear and the speed sensor reads on the output shaft so the speedometer remained correct.