1998 Mustang 3.8L V6

So, trying to trouble shoot this issue, thought I had figured it out.

Bought the car near the beginning of May 2016.

the temp, fuel, battery & oil pressure all work fine in original instrument cluster.

Picked up instrument cluster from a junk yard, but it had a different trace than what is on the original instrument cluster.

Took the 2 instrument cluster's apart and replaced the center speed and rpm section out of the new cluster and installed it in the original casing cluster.

after driving it around for a blocks, the odometer & trip Meter started working for about 1000 miles.

now it has stopped working? could it be a sensor? is there something connected to the transmission or engine?

there are only 2 wiring harnesses going to the instrument cluster.

any help would be appreciated!