4L80 Stuck in 2nd Gear

[Mogman]

There is a power relay somewhere for the TCM, follow that wire from the fuse with the red leads going into that plastic wire loom, that wire loom would not be what I would expect but there must be a wire leading from the connection between the batteries (12V tap) to the TCM and power relay for the TCM to work.
OH yes,,, I completely agree with Mullaney that the entire electrical system needs maintenance, I would be ashamed to turn over a vehicle to a customer looking like that.

 

[4x4nutz]

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It's no fun, but looking at that 4th picture - I think some good old fashioned elbow grease and some anti-oxidizing paste would help. If that looks that way then my guess there are other places that look the same. Disconnecting the battery terminals before you start might be really smart. No need to let the smoke out of your truck for no good reason.

Invest a full weekend. About 16 hours. From bumper to bumper.
A lot of things will be solved with a wire brush or a tooth brush and some cleaner...

There is a power relay somewhere for the TCM, follow that wire from the fuse with the red leads going into that plastic wire loom, that wire loom would not be what I would expect but there must be a wire leading from the connection between the batteries (12V tap) to the TCM and power relay for the TCM to work.
OH yes,,, I completely agree with Mullaney that the entire electrical system needs maintenance, I would be ashamed to turn over a vehicle to a customer looking like that.

The fuse? Do you mean the wiring from the power and negative poles near the batteries?? I've only seen fuses in M1123's, and up to 1167's. This is an 1097 that was upgraded from a 3 speed to a 4 speed.

 

[Milcommoguy]

Pictured is the 24 volt buss. The other thingie that looks like a fuse is a shunt.

Shunt. A calibrated resistor for measuring current, CAMO

 

[Mogman]

The fuse located in your second picture above, I am sorry I did not know this truck had been "ungraded", the manual is pretty much useless you have to figure out what the guys doing the upgrade did, but one thing is for sure, the TCM/trans runs on 12V that aftermarket fuse lying on top of the batteries is the beginning of your journey...

 

[Coug]

So in your 5th picture there is the 200 amp umbilical plugs behind the battery box.
Between that plate in the rear footwell, and the battery box, that is where a circuit breaker goes in the 4 speed trucks. It's not in any of your pictures because in your case you may need to remove the plate in the rear footwell to see it. Might be able to see it looking straight down behind the battery box.

 

[Mogman]

This blade fuse laying on the batteries.

 

[4x4nutz]

The fuse? Do you mean the wiring from the power and negative poles near the batteries?? I've only seen fuses in M1123's, and up to 1167's. This is an 1097 that was upgraded from a 3 speed to a 4 speed.

This blade fuse laying on the batteries.
View attachment 889360

That's for a aftermarket horn.

 

[4x4nutz]

So in your 5th picture there is the 200 amp umbilical plugs behind the battery box.
Between that plate in the rear footwell, and the battery box, that is where a circuit breaker goes in the 4 speed trucks. It's not in any of your pictures because in your case you may need to remove the plate in the rear footwell to see it. Might be able to see it looking straight down behind the battery box.

You are right....that's where it was.

 

[Mogman]

I just do not see any other 12V connection in your picture, the pic does not completely show the connection between the batteries, there must be a 12V feed to the transmission, maybe I just cannot see it.
So they just left the breaker flopping around?

 

[4x4nutz]

I just do not see any other 12V connection in your picture, the pic does not completely show the connection between the batteries, there must be a 12V feed to the transmission, maybe I just cannot see it.
So they just left the breaker flopping around?

No, it was well hidden between two panels with no access. I took everything apart to get to it.

 

[Autonomy_Lost]

The thick wire thats taped off....pull off the tape and look for a tag that says 290/291.

Thats what was disconnected on mine. Connect it to the 12v tap (pos terminal of rear battery).

I think they just dont bother hooking that up when they install the cheap batteries on auction trucks.

 

[4x4nutz]

The thick wire thats taped off....pull off the tape and look for a tag that says 290/291.

Thats what was disconnected on mine. Connect it to the 12v tap (pos terminal of rear battery).

I think they just dont bother hooking that up when they install the cheap batteries on auction trucks.

Dude!!!! I will check it tomorrow....why in hell would they cut and tape off a wire that keep the tranny working?

 

[4x4nutz]

Dude!!!! I will check it tomorrow....why in hell would they cut and tape off a wire that keep the tranny working?

The thick wire thats taped off....pull off the tape and look for a tag that says 290/291.

Thats what was disconnected on mine. Connect it to the 12v tap (pos terminal of rear battery).

I think they just dont bother hooking that up when they install the cheap batteries on auction trucks.

I tore off the old tape and there was no tag on that fat wire bundled with the 57T and 599C. The tags may have been cut off as the fat wire looks short. Are you fairly certain I can connect this fat wire to the posi on the rear battery?

 

[Autonomy_Lost]

Dude!!!! I will check it tomorrow....why in hell would they cut and tape off a wire that keep the tranny working?

You're lucky they even installed batteries! Mine had NO air filter installed, and the alternator only had one bolt installed. The seats were held in with gravity and good luck.

The people "working on" these trucks simply do not care what your experience is lol.

 

[Autonomy_Lost]

I tore off the old tape and there was no tag on that fat wire bundled with the 57T and 599C. The tags may have been cut off as the fat wire looks short. Are you fairly certain I can connect this fat wire to the posi on the rear battery?

Without the tag I can't say for certain. But mine looks exactly like yours with the one big wire and 2 small wires. It was the big one that was disconnected. If you give me a minute I can check the tags on the 2 little wires.

Its your truck though, I'm just same random guy on the internet and I'm no expert. Proceed with caution and I take no responsibility if you fry something

 

[Autonomy_Lost]

Okay, my little 2 wires are 57R and 599C, so same circuit as your 2 little wires.

Again, the big wire is labeled 290/291 and thats what was disconnected on mine. I hooked it up to 12v and my transmission started working (and the trans light started working as well).

IF you decide to try this, I would start by putting the start lever on RUN and see if the trans light comes on, before starting anything.

Again, proceed at your own risk, and acknowledge that you aren't really following proper troubleshooting steps here. The safer approach is trace out all of the wires, see where they go, and consult the TM's.

 

[4x4nutz]

Okay, my little 2 wires are 57R and 599C, so same circuit as your 2 little wires.

Again, the big wire is labeled 290/291 and thats what was disconnected on mine. I hooked it up to 12v and my transmission started working (and the trans light started working as well).

IF you decide to try this, I would start by putting the start lever on RUN and see if the trans light comes on, before starting anything.

Again, proceed at your own risk, and acknowledge that you aren't really following proper troubleshooting steps here. The safer approach is trace out all of the wires, see where they go, and consult the TM's.

Wow! I did get a note from a guy at Fort Hood who said their motor pool had purposely kept some of their humvees in limp mode per a directive to keep the grunts from going over 30 MPH on base and wrecking shit. Thank you for the help.

 

[Mogman]

It necessarily must have a tap for the 12V, that connection has to be between the two batteries, what I am saying is I only see the wire/fuse to the aftermarket equipment, I do not see any other tap..
Check the schematic on the file I listed and see if you have that wire connected.

No, it was well hidden between two panels with no access. I took everything apart to get to it.

 

[4x4nutz]

It necessarily must have a tap for the 12V, that connection has to be between the two batteries, what I am saying is I only see the wire/fuse to the aftermarket equipment, I do not see any other tap..
Check the schematic on the file I listed and see if you have that wire connected.

Will check. Thank you brother!

 

[frauhansen]

Nice to hear you going forwad. attached a picture of the switch in my rig.

Behind tge passanger seat