Tour Master Transmission Issue today. Bad module?

[proost]

Hey y'all. Travel days. �� Had a transmission issue today that I believe is electronic on our 2007 Tour Master T40A. Allison 6-speed (edit).

The control pad would reboot and the speedometer would cycle to zero and then back up again while the shift control pad 'rebooted'. At one point, we had a "TRANS ECU NO DATA" error flash up on the Freightliner display on the dash but no codes. We swung into a Freightliner Oasis shop and they said that without any codes, it's on the Allison side, not the chassis.

Driving today, I noticed a few predictable symptoms:
- When the problem happens, the shift control pad would power cycle (go dark -> all readout leds would light up and then it would show the gear status) and the speedometer would drop to zero and then back to the speed and repeat until the pad would reset.
- this issue happens from a stop in 1st if the RPMs go higher (2000rpm+) (it also goes into neutral)
- it also happens when down shifting from and and upshifting to 5th. Again, it happens usually if the RPMs are above 2000rpm. We made it to our destination watching that because I could take it easy on the throttle and avoiding these. No problems with the transmission in any gear other than the cycling issue at those points.

Any ideas? My gut says it could be the TCM/ECM. Does anyone know where that module is or has experienced something like this? Looking for maybe a loose wire, etc. I've heard under the control pad on the driver's left or somewhere else including on the transmission itself.

Thanks in advance!

 

[proost]

Wanted to close out this issue as well. It turned out that the exterior transmission harness that connects all of the sensors to the TCM had frayed in a few spots. A lot of loose wires inside the loom which is hard plastic and there you have it. I ultimately took it an authorized Allison service center and their electronics tech pulled the harness out, fixed one severed 12V power supply line and repaired a bunch of other frayed lines. Then, he wrapped it all in Matco Tera Anti-abrasion tape and reinstalled. Fixed!

Apparently, there are two 12V power supply wires to the TCM in that harness and because one of them was severed, the TCM had a useful voltage/amperage lower than what my battery was providing. Somehow, on that trip, my voltage regulator kicked off and my battery voltage dropped revealing the harness issue and the symptoms that I was seeing on the road. Consequently, the day before I took it in I topped off my batteries and the problem I was experiencing went away even though it was still there.

Aaaand, now I'm a lot smarter on the Allison! ��