6L80 Shifting Issues

[duanejacques]

does anyone know about the 6L80 that came in the M1151A1? I seem to have an issue with the shifting = meaning that it seems to need some accelerator pedal release each time I need a higher gear. The fluid is fine and red. I serviced it with a new filter and re=usable gasket. One note is that the gauge panel is missing and I was wondering if the electronic speedo had any input into the transmission control box. I was thinking that it had no idea where the pedal or speed was. It seems to be the same wether I am in overdrive or any other position. It is quiet similar to a new trans etc

 

[Mogman]

I do not think a 6L80 was ever put in a HMMWV from the factory. (I did though)
It should be a 4L80E
Here is the troubleshooting guide
The first thing you need to do is check the codes, second measure the TPS voltage.

 

[duanejacques]

Yes sir you are right it's a 4l80

 

[Mogman]

The first thing I do is make sure the trans light comes on when the run switch is put into run position, engine not running.
If not unplug the wire harness from the glow plug TSU (temp sending unit) so more testing will not fry the glow plugs, passenger side of the front water cross over.
If you do not have this light working as described you must first figure out why before moving on,
The most common issue would be..
Power to the TCM, it has two 12V sources, one hot all the time and one switched by the run switch.
Bad trans lamp or wiring to lamp.
Bad ground to the TCM.
Bad, missing TCM, open it up and look for water damage.
Then after getting a trans light then you can start troubleshooting your transmission.
All the schematics that you need are in the attached troubleshooting guide.

 

[duanejacques]

The first thing I do is make sure the trans light comes on when the run switch is put into run position, engine not running.
If not unplug the wire harness from the glow plug TSU (temp sending unit) so more testing will not fry the glow plugs, passenger side of the front water cross over.
If you do not have this light working as described you must first figure out why before moving on,
The most common issue would be..
Power to the TCM, it has two 12V sources, one hot all the time and one switched by the run switch.
Bad trans lamp or wiring to lamp.
Bad ground to the TCM.
Bad, missing TCM, open it up and look for water damage.
Then after getting a trans light then you can start troubleshooting your transmission.
All the schematics that you need are in the attached troubleshooting guide.

Yes I definitely have the yellow trans light. It comes on with the run lever and goes off after starting. I will do the troubleshooting that you have sent me and let you know what I find. I was kind of concerned about also still having the missing gauge panel since some obvious grounds are just hanging free. Ty

 

[Mogman]

I have never tried with the panel out but cannot think of any reason the trans would not work, at least to the point you can read the codes which would be next.
The grounds for the transmission sensors should be grounded back to the TCM, looking at the schematics nothing is obviously dependent on the inst. panel.
Although you should not be running it without the panel let alone trying to drive it as you cannot monitor vital things like oil pressure, water temp and voltage

 

[duanejacques]

Sorry it's been a while, so finally, I had a good 12 code flash for the transmission control module test. I have also found a couple of other things wrong, e-brake was dragging, and I re adjusted the TPS at the IP. I have also changed the Transmission Control Module 2100-AB to a new date code . Perfect shifts. I am sure that a combination of these things definitely set me back. Thank you for all your knowledge and help with this. I have since acquired 5 additional models of hmmvw and have 3 that ,after working on them, run fine. The other two are running great but have problems I'm trying to figure out.

 

[duanejacques]