This truck is stuck in park unless you bypass the lock out. It also is stuck in 2nd gear as it drives. According to the owner, the truck had issues similar to this before and it was a wiring issue that was repaired. There's also trans oil in the large round plug connector as well.

I don't have much information on these HD trucks, does anyone have a line on an electrical schematic for the Allison? Or any info on what may be a problem area with these transmissions? I have talked to a few tranny guys and they state the trans control module is a culprit on these. Any direction or information would be much appreciated!!!

Gary Grimler
Owner
Grimler Automotive & Performance
Highland, Indiana, USA