M936A2 Wrecker - Transmission won't work in reverse

[Vislocky]

I have a M936A2 5-ton wrecker. The transmission moves well in all forward gears. The transmission tries to move in reverse but will only move a short distance and that is a struggle. I have changed the canister transmission oil filter, the internal flat transmission filter, and the transmission governor filter. The transmission fluid was changed with Cam2 Super Synthetic Heavy Duty Automatic Transmission Fluid (10W) and still no change in reverse. The transmission appeared to have a heavier weight oil in it, possibly 10W40.

Any ideas what is wrong and what I can try to fix this problem? Thank you!!

 

[Jbulach]

Is the transfercase in high range?

 

[glcaines]

I have a M936A2 5-ton wrecker. The transmission moves well in all forward gears. The transmission tries to move in reverse but will only move a short distance and that is a struggle. I have changed the canister transmission oil filter, the internal flat transmission filter, and the transmission governor filter. The transmission fluid was changed with Cam2 Super Synthetic Heavy Duty Automatic Transmission Fluid (10W) and still no change in reverse. The transmission appeared to have a heavier weight oil in it, possibly 10W40.
Any ideas what is wrong and what I can try to fix this problem? Thank you!!

When you say the transmission tries to move in reverse, is the transmission slipping? Does the engine lug down while trying to go in reverse? Perhaps the parking brake is locking up in reverse? I had that happen once in a deuce I previously owned when a spring in the parking brake broke.

 

[Vislocky]

Is the transfercase in high range?

Yes, in high range. I was told not to back up in low range.

 

[Vislocky]

When you say the transmission tries to move in reverse, is the transmission slipping? Does the engine lug down while trying to go in reverse? Perhaps the parking brake is locking up in reverse? I had that happen once in a deuce I previously owned when a spring in the parking brake broke.

The engine increases in RPM as you give it gas but the truck does not want to move. The transmission acts like it is slipping. It will move some in reverse but any kind of incline and it won't move. The parking brake seems to be releasing properly and the truck moves forward with no problem and goes through the gears with no problem all the way up to cruise speeds. It is just the reverse... it acts like its not getting any fluid or the bands are slipping... but one would think if it moves forward with no problem, it would move in reverse to. I do not know anything about an Allison transmission.

 

[simp5782]