I bought this flatbed at auction about a month ago, couldn't pass it up for the price. 12v cummins with 177,000 mi. It was part of a seal coating fleet but its in damn good condition for the year. Nearly rust free... plus its a flatbed .

So I finally go to drive it home and notice it shifts good all up until its supposed to "lock up" and if I give it more throttle it acts like its in neutral and rpms rack up. When its in 4th gear the rpms are at 2250 - 2500 rpm. disengaging o/d via the dash button doesn't seem to help. Ive done a lot of research on what it could possibly be but nothing has fixed the issue. I wired in a toggle switch for the TC lockup, but it wasn't doing anything. I was up to speed when i engaged it, so I checked to make sure i had a good 12v ground source to the switch, I do. So for S&G I took my test light and probed the black/orange wire that I tied into from the pcm (pin 54) and coming straight out of the pcm the black/orange wire is already grounded. Do I need a new pcm? Any help would be great.

Im also having trouble with the tach dropping out. Sometimes it works and sometimes it doesnt. Ive cleaned and re-gapped the crank sensor all was good so i thought until it dropped out again. i can tell its not the oem crank sensor and is a advanced auto special but it does work.. at times.. im not as concerned with that as i am the tranny.

 

well I got the T/C kill switch to work... just doesn't seem right. 2500rpm in lockup?