NEWS | Nov. 30, 2020

HMMWV: Transmission Failure Fix

Dear Half Mast,

The unit I’m with has eight (8) M1165 HMMWVs. The transmissions are completely burned out in five (5) of the vehicles after only being driven 300 miles annually.

Are there any updates or known issues with these variants and if so, is there a solution? My concern is this may be happening because the vehicles aren’t being driven much and there’s little to no communication between the batteries and the transmission control module (TCM).                                                            
                                                                                          
SSG C. T.   

Dear Sergeant C.T.,

TACOM knows about the transmission failure issue and is researching why it’s happening.

The known reason for the failure is covered in TACOM Maintenance Action Message 11-041 regarding slave starting. Units should follow the guidelines in the MAM because improper slave starting leads to voltage spikes, resulting in transmission failures.

Another possible cause relates to operators driving the trucks in LIMP mode without knowing it. You can get up to 40-45 mph while the vehicle is in second gear. That puts stress on the transmission.

Finally, TCM failure will cause the transmission warning light inside the truck to stop working. If the warning light doesn’t work, then drivers may think there are no issues and drive too fast while in LIMP mode.

Until further guidance is available, check out TACOM MAM 11-041 for more info (requires CAC to access):   



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