2010 6.5 4l80 gets to 50 no overdrive and no trans light

[deshet]

Hi all,
And thanks in advance for any help provider.
This is my first Humvee.
2010 6.5 4l80 gets to 50 mph no overdrive and no transmission light with key on or running.
If I put transfer case in HL that light lights up
I have downloaded the transmission manual and I am looking through that to see if I can figure things out.
Vehicle has 3,000 mi
transmission fluid looks good
Hoping that this points to something that may be easily identified
Thanks

 

[Mogman]

The first thing you need to is get that trans light working and see if there are any codes.
So you do have the "transmission supplement"?

 

[deshet]

Yes I have the transmission manual I found it in one of your previous posts
Is there a common wire that gets cut that I should zero in on.

Thanks

 

[Mogman]

Yes I have the transmission manual I found it in one of your previous posts
Is there a common wire that gets cut that I should zero in on.

Thanks

If the TCM is getting enough power that it is shifting then it is usually the lamp or the wires to the lamp.
Wire number 675B should be hot with 12V all the time, the other grounds in the TCM to turn the light on.
IIRC the "hot" (12V) is the contact in the harness plug that the light is plugged into is protected from shorting than the other contact.
You will understand when you look at the plug, and yes they could have made that harness a few inches longer....

 

[mrfarb]

To piggyback on Mogmans suggestion, are you certain the transmission is shifting at all? I went through this with an A2 4 speed truck - limp mode starts in 2nd gear and won’t shift at all. Basics - manually shift first to second. I bet you aren’t getting power to the TCM, it’s common.

 

[Retiredwarhorses]

NO TCM lamp? No shifting of the transmission, the lamp lit during startup is a “Hey, I see the TCM”
A lamp that doesnt extinguish while running, is a TCM that does not see the motor running…
check power to the TCM at the batteries

 

[Mogman]

Are you sure it is just not shifting into OD or are you saying it does not shift at all??

 

[deshet]

Is normal operation for the trans light to stay on.
This is my first Humvee.
I'm using group 65 batteries.
The factory leads were not long enough and once I installed those properly I got the transmission light. It still doesn't shift into overdrive as I believe it should.
The transmission light stays on continuously.
Engine RPMs are pretty high above 40.
It seems to have shift a little better, The way I had the batteries connected previously.
Just had a straight cable going between the two groups 65 batteries positive negative to make a parallel connection.

The Humvee factory cable has a few leads off of it that we're not previously hooked up. Once those were hooked up the transl now comes on.

I have seen other post about switching solenoids on the transmission, seems like one is not used.

I will see if I can get any codes from the transmission.

Any other recommendations?

The fluid is full and looks clean.



Thanks

 

[Coug]

max speed 50 and high RPMs is in limp mode and not shifting at all (stuck in 2nd gear)
There is also a circuit breaker behind the battery box with a button that sticks out. Try pushing in button and seeing if that changes anything. Use meter to check and see if you have 12V both into and out of that breaker.

 

[Mogman]

Is normal operation for the trans light to stay on.
This is my first Humvee.
I'm using group 65 batteries.
The factory leads were not long enough and once I installed those properly I got the transmission light. It still doesn't shift into overdrive as I believe it should.
The transmission light stays on continuously.
Engine RPMs are pretty high above 40.
It seems to have shift a little better, The way I had the batteries connected previously.
Just had a straight cable going between the two groups 65 batteries positive negative to make a parallel connection.

The Humvee factory cable has a few leads off of it that we're not previously hooked up. Once those were hooked up the transl now comes on.

I have seen other post about switching solenoids on the transmission, seems like one is not used.

I will see if I can get any codes from the transmission.

Any other recommendations?

The fluid is full and looks clean.



Thanks

You are stuck in limp mode as pointed out above, read the supplement about putting a jumper on the acc plug at the TCM and read the codes.
I was confused as you were saying it shifted but would not go into OD
EDIT it is on page 60.
Here is the pinout of the acc connector you jump A to E simple as that.

 

[Retiredwarhorses]

Is normal operation for the trans light to stay on.
This is my first Humvee.
I'm using group 65 batteries.
The factory leads were not long enough and once I installed those properly I got the transmission light. It still doesn't shift into overdrive as I believe it should.
The transmission light stays on continuously.
Engine RPMs are pretty high above 40.
It seems to have shift a little better, The way I had the batteries connected previously.
Just had a straight cable going between the two groups 65 batteries positive negative to make a parallel connection.

The Humvee factory cable has a few leads off of it that we're not previously hooked up. Once those were hooked up the transl now comes on.

I have seen other post about switching solenoids on the transmission, seems like one is not used.

I will see if I can get any codes from the transmission.

Any other recommendations?

The fluid is full and looks clean.



Thanks

first off, stop driving the truck around at 4k RPM…you can test shifting with just normal down the street for a short distance, your transmission is in 2nd gear limp mode, it’s not meant to run down the freeway at 50mph, it’s meant to get to a safe spot an pull over.
the transmission lamp staying on means the TCM doesn’t see the engine runnin, that’s a CPS issue…check to make sure the CPS is plugged in to the harness.

 

[deshet]

Not really sure what made anyone jump to the conclusion that the truck was being driven on the interstate. But I really appreciate the support. This is my first humvee and I am figuring things out.

Thanks for reporting on the standard light operation

Not my first diesel or 10th 6.5.

Not an expert or an idiot,

will use the jumper to pull codes.

I really appreciate the support.

Thanks

 

[Retiredwarhorses]

Not really sure what made anyone jump to the conclusion that the truck was being driven on the interstate. But I really appreciate the support. This is my first humvee and I am figuring things out.

Thanks for reporting on the standard light operation

Not my first diesel or 10th 6.5.

Not an expert or an idiot,

will use the jumper to pull codes.

I really appreciate the support.

Thanks

50mph was you’re statement…not mine, so a freeway, interstate , back road, do we really need to get that granular…
Daily now I’m seeing folks post only after damage is incurred before asking the basics of questions on how to prepare these trucks for
a maiden voyage.
So like many others newbs here who can’t handle anything but a response that’s garnered In snow flakes…have at it.

 

[deshet]

Newb ok, I have had an account on this site dating back to the early-mid 2000s. Seems like someone has Internet courage. The type they lack in real life.

If you don't have interest in helping people then don't post. I am not going to bow down to anyone for a little guidance

Back to the topic and please accept my apologies for those that are trying to help.

The CPS is connected in the process of getting the codes.

Thanks

 

[Mullaney]

Newb ok, I have had an account on this site dating back to the early-mid 2000s. Seems like someone has Internet courage. The type they lack in real life.

If you don't have interest in helping people then don't post. I am not going to bow down to anyone for a little guidance

Back to the topic and please accept my apologies for those that are trying to help.

The CPS is connected in the process of getting the codes.

Thanks

.
It might be worth the effort to Anti-Ox and clean the connectors with a stiff bristle brush.

 

[deshet]

I updated my signature to show this vehicle.
My transmission plug isn't a 9 pin.
Transmission light goes out when I disconnect this plug picture attached.
I'm currently under the vehicle and I don't see any cut wires or anything that's missing everything looks to in the factory location.

This is the second one on the trailer, right in the middle

I will see if I can locate a newer manual for this vehicle.

I appreciate the support and will try to spray some electrical cleaner in the plug.

Thanks

 

[Mogman]

I updated my signature to show this vehicle.
My transmission plug isn't a 9 pin.
Transmission light goes out when I disconnect this plug picture attached
I'm currently under the vehicle and I don't see any cut wires or anything that's missing everything looks to in the factory location.

This is the second one on the trailer, right in the middle

I will see if I can locate a newer manual for this vehicle.

I appreciate the support and will try to spray some electrical cleaner in the plug.

ThanksView attachment 927550

There are two plugs on the TCM box, use the other one, the harness must be connected.
Also by disconnecting that harness you have erased any stored codes.

 

[deshet]

I figured it out pulling codes now.
I was looking at the manual and looking for a cable that is for a specific diagnostic tool based on the pictures.

 

[deshet]

Code 73
Pressure control solenoid circuit.
Validated that all the cannon plugs are connected
Will check the ohms between g and k on the j-1 connector and report back
Thanks

 

[Mogman]

Code 73
Pressure control solenoid circuit.
Validated that all the cannon plugs are connected
Will check the ohms between g and k on the j-1 connector and report back
Thanks

You might want to inspect the connector at the trans for fluid in the connector.
But the internal (transmission) harnesses also fail as could the valve solenoid.