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Aroadracer · 09-26-2020, 12:10 PM

I’m traveling to CO through Albuquerque today and heard a clunk and the transmission display went blank. The check transmission light is on. It is running and stuck in I believe 3rd gear. Of course it’s Saturday and no Allison or Catapillar shops are open. Does anyone have a suggestion on how to reset or troubleshoot with no display? I’m reluctant to turn it off as I do t know if it will restart in gear.

Smitty77 · 09-26-2020, 03:16 PM

The mechanical sound is what makes this hard really help much... Usually, a mechanical sound comes along with a mechanical problem

! (Hope I'm wrong.).

You might try disconnecting the Chassis Battery cable at the terminal for about 15 minutes, and see if that resets the Allison ECM.

And I'd suggest you ask this to be moved to the Allison part of the forum, under Powertrain Garage... As it should not be unique to a CC.

Best of luck, and please let us know what you find out,
Smitty

wolfe10 · 09-26-2020, 03:19 PM

What YOU can do after you are in a safe place to stop and engine OFF:

Unplug and re-plug the gang plugs on the Allison ECU. If shift pad separate, do the same for the plug on that end.

Then check for 12 VDC to the TWO fuses supplying the Allison (the smaller one is for memory, the larger one for powering it while running.

If you can get any display, check for diagnostic codes (using shift pad).

You don't say what year your coach is, so diagnostic procedure choices:

If older, ignition on, engine off. Push up and down arrows at the same time. That will bring up d-1 and any code. If there is a diagnostic code, push mode to bring up the next diagnostic code. Repeat until you get d-"whatever" and - -.

If newer, pushing the up and down arrows at the same time will bring up OL (for oil level). Push the up and down arrows again to bring up the diagnostic codes as above.

Aroadracer · 09-27-2020, 06:54 AM

Update: I talked to an RV tech with my goodsam road side assistance policy and he advised turning off the engine and disconnecting the positive battery cables from the chassis batteries and leaving unconnected for one hour. I reconnected and turned the key to the first position and the shifter display appeared! I did the diagnostic checks by pressing the arrow buttons and got oil level ok and no error codes. Decided to continue on to silverton and we made it with no issues. The transmission did seem to hunt back and forth under certain conditions, kind of erratic like it couldn’t decide which gear to be in but when the grade or speed changed it would stabilize. It’s a 1999 Affinity with a CAT C12. Going up the passes I would manually down shift to keep the revs up and that worked fine.

wolfe10 · 09-27-2020, 07:07 AM

Quote:

Originally Posted by Aroadracer

UThe transmission did seem to hunt back and forth under certain conditions, kind of erratic like it couldn’t decide which gear to be in but when the grade or speed changed it would stabilize.

Anytime any transmission "hunts" between gears, down arrow/down shift to the lower gear and back out of the throttle a little to maintain that higher RPM. Better cooling and better on the transmission.

Hunting is not that unusual in any heavy vehicle-- there will be plenty of grades where power in the lower gear is enough that it upshifts, but not enough power that it can hold the higher gear.

And, I suspect that this will be even more of an issue for the new 8-10 speed transmissions!