Kevin Donahue
Member
- 58
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- 8
- Location
- Chesterfield
Howdy,
I've got an M1123 Humvee with the 4L80E. Fighting a weird issue where the Transmission basically free wheels in reverse (meaning it feels like it's in neutral) but only after driving for at least 30 minutes or so. The longer I drive and the faster I go the worse the condition gets. A quick 10 min drive on back roads to the gas station for instance causes no symptoms, but a 45-minute highway commute to work and I can barely move in reverse/ not move at all.
All forward gears work great. In fact, even when the reverse gear is in full slip mode, I can rock crawl in forward gears and have no slippage.
I took the pan off to verify the reverse band servo (or whatever it's called) travel and it appears to be in spec and basically new (no wear). I was hoping the fix that involves slightly lengthening the rod which pushed on the band would fix this but that doesn't appear to be necessary for mine. I also did the test where I put it in 4low and 1st gear to verify whether or not there is engine braking and it appears there is normal engine braking. This also indicates the servo is functioning properly based on what I've read.
Finally, I ran the TCM diagnostic test and got a 52 code which indicates prolonged high voltage to the TCM. I haven't checked grounds but will do so soon and probably add a supplementary grounding harness. Other than a bad ground, I am not sure what to look for in regard to high voltage and whether or not this would even have anything to do with the reverse which seems to be all mechanical.
Any advice, past experience with this would be extremely helpful! Thanks in advance!
I've got an M1123 Humvee with the 4L80E. Fighting a weird issue where the Transmission basically free wheels in reverse (meaning it feels like it's in neutral) but only after driving for at least 30 minutes or so. The longer I drive and the faster I go the worse the condition gets. A quick 10 min drive on back roads to the gas station for instance causes no symptoms, but a 45-minute highway commute to work and I can barely move in reverse/ not move at all.
All forward gears work great. In fact, even when the reverse gear is in full slip mode, I can rock crawl in forward gears and have no slippage.
I took the pan off to verify the reverse band servo (or whatever it's called) travel and it appears to be in spec and basically new (no wear). I was hoping the fix that involves slightly lengthening the rod which pushed on the band would fix this but that doesn't appear to be necessary for mine. I also did the test where I put it in 4low and 1st gear to verify whether or not there is engine braking and it appears there is normal engine braking. This also indicates the servo is functioning properly based on what I've read.
Finally, I ran the TCM diagnostic test and got a 52 code which indicates prolonged high voltage to the TCM. I haven't checked grounds but will do so soon and probably add a supplementary grounding harness. Other than a bad ground, I am not sure what to look for in regard to high voltage and whether or not this would even have anything to do with the reverse which seems to be all mechanical.
Any advice, past experience with this would be extremely helpful! Thanks in advance!