Where is the Transmission Control valve located?

[Chad Lares]

I'm trying to figure out why one of my M1097A1 barely moves when I put it in gear. Engine racing and the thing is just crawling like a turtle. I looked up some references talking about checking this transmission control valve and making sure it isn't stuck. Fine, where is it? I can't find any reference pointing to its actual location. I opened up the transmission pan, couldn't see it. Does anyone have a picture of where it is located? Explain to me, with pictures preferably, like you would show the dumbest of dogs where his water dish is at.

I think this is the part: https://www.easternsurplus.net/PartDetails/9746/HM-1601-Transmission-Pressure-Control-Valve-HMMWV

 

[Mogman]

In the valve body accessible by removing the pan and filter.
Google is your friend.

 

[TOBASH]

1-ensure transfer case is not in “L”

2-look up tranny tm and jumper J2 port A-E and write down the codes. (You will understand what I am talking about once you read the technical manual.)

https://www.steelsoldiers.com/attachments/4l80e-transmission-troubleshooting-tcm-supplement_7-pdf.903367/

 

[Mogman]

How did the fluid look? was it bright red or more of a blood color?? was there any friction material in the pan??
Sounds like the trans might be toast

 

[Chad Lares]

https://youtube.com/shorts/zfCCzakz490?feature=share

Here's a video of the pan opened up.

 

[Mogman]

If you get to the point that you have the pan back on you can unplug the TCM.
With the TCM connected it will try to pull in 1st gear unless you have a problem that is putting the trans in limp mode, with the TCM disconnected it will try to pull in 2nd gear, I have seen a 4L80 that would not pull with the TCM connected but would with it disconnected because the 1st gear clutches were totally burned out.
It should work in reverse in ether case.
Did you pull the codes from the TCM? this of course should be the first thing anyone should do when troubleshooting transmission problems.

 

[Chad Lares]

If you get to the point that you have the pan back on you can unplug the TCM.
With the TCM connected it will try to pull in 1st gear unless you have a problem that is putting the trans in limp mode, with the TCM disconnected it will try to pull in 2nd gear, I have seen a 4L80 that would not pull with the TCM connected but would with it disconnected because the 1st gear clutches were totally burned out.
It should work in reverse in ether case.
Did you pull the codes from the TCM? this of course should be the first thing anyone should do when troubleshooting transmission problems.

It's a 1996 M1097A1 with a 3 speed transmission. No TCM to pull codes off of or any flashing lights like the 2003 model I got going late last year.

 

[Mogman]

It's a 1996 M1097A1 with a 3 speed transmission. No TCM to pull codes off of or any flashing lights like the 2003 model I got going late last year.

Sorry, I completely missed the A1 part
Does it pull in reverse?
The 2-3 valve is in the valve body, you would have to pull the valve body to get access IIRC.
Those things are pretty much bullet proof until they are toast, again was there any metallic or clutch material in the pan?

 

[Chad Lares]

Sorry, I completely missed the A1 part
Does it pull in reverse?
The 2-3 valve is in the valve body, you would have to pull the valve body to get access IIRC.
Those things are pretty much bullet proof until they are toast, again was there any metallic or clutch material in the pan?

No metal shaving at all. No burnt smell either. OK, So I have to further take that thing apart and it's on the inside.

 

[Chad Lares]

Here's a video of it barely moving when put into gear. No metal shavings in pan, no burnt smell. New fluid.

 

[TOBASH]

Very low transmission fluid will do the same thing.

Burnt out clutch pads will do the same thing.

Best is to fill to full and follow the Tammy TM as previously posted for you.

 

[TOBASH]

It's a 1996 M1097A1 with a 3 speed transmission. No TCM to pull codes off of or any flashing lights like the 2003 model I got going late last year.

Ok. In the future, always post the year of your vehicle and the transmission type and engine type. Might be good to put it in your signature.

You have a turbo hydromatic 400. Totally mechanical transmission. That is the most bulletproof transmission ever manufactured by GM.

Make sure your transmission level is full. If you still have a problem, l bet you should rebuild the transmission because the clutch plates are probably burnt out. That is assuming that there is no problem with your transfer case and your console shifter is properly adjusted.

 

[Mogman]

https://youtube.com/shorts/zfCCzakz490?feature=share

Here's a video of the pan opened up.

That is the "passing" valve, it would have a switch on the IP that would send voltage to it at WOT and would have nothing to do with your problems.
There is nothing electronic about the 3L80 as far as pressure control etc.

 

[Mogman]

Have you tried putting the transfer case in 4lo or HL?
The trans itself is as I said fairly simple, if it has fluid and a clean filter but will not pull it is probably a mechanical issue you are not going to be able to resolve.

I'm trying to figure out why one of my M1097A1 barely moves when I put it in gear. Engine racing and the thing is just crawling like a turtle. I looked up some references talking about checking this transmission control valve and making sure it isn't stuck. Fine, where is it? I can't find any reference pointing to its actual location. I opened up the transmission pan, couldn't see it. Does anyone have a picture of where it is located? Explain to me, with pictures preferably, like you would show the dumbest of dogs where his water dish is at.

I think this is the part: https://www.easternsurplus.net/PartDetails/9746/HM-1601-Transmission-Pressure-Control-Valve-HMMWV

View attachment 925623

I think the reason we all went for the 4L80 is because I think this is not the troubleshooting steps for a 3L80, and the fact you thought it had a pressure control valve.

 

[Chad Lares]

Have you tried putting the transfer case in 4lo or HL?
The trans itself is as I said fairly simple, if it has fluid and a clean filter but will not pull it is probably a mechanical issue you are not going to be able to resolve.

I think the reason we all went for the 4L80 is because I think this is not the troubleshooting steps for a 3L80, and the fact you thought it had a pressure control valve.

It's a 1996 M1097R1, not A1. No, after tearing everything apart, there is NO pressure control valve anywhere. Chasing my tail thinking I'm following the manual only to find out the hard way that although referenced in the manual, it's simply not on this vehicle. Now I'm back to the beginning trying to figure out why it's not shifting correctly. No metal shavings, no burned out smell, fluid is clean. Just do not know other than replacing the entire transmission. Very frustrating.

 

[Mogman]

It's a 1996 M1097R1, not A1. No, after tearing everything apart, there is NO pressure control valve anywhere. Chasing my tail thinking I'm following the manual only to find out the hard way that although referenced in the manual, it's simply not on this vehicle. Now I'm back to the beginning trying to figure out why it's not shifting correctly. No metal shavings, no burned out smell, fluid is clean. Just do not know other than replacing the entire transmission. Very frustrating.

Well you called it an A1 in the first post, R1/A1 makes no difference if it is a 3 speed, as I said I did not think you were using the correct troubleshooting guide.
If there is no indication of failure, fluid, particles in the pan etc. I would put it back together and make sure it is not a transfer case, diff, axle problem.
Putting it in HL or L will "bypass" a failed diff or half shaft.
Other than that there is very little you can do if the trans will not pull as the transmission is strictly mechanical.
Any competent trans shop should be able to troubleshoot the trans by checking pressures etc but if the trans will not pull then it is almost certain it will have to come out.
The good is you can likely find a good pulled transmission, heck I have tossed good ones out in the pasture to rot down because I just don't have room in my shop to store them.

 

[Coug]

It's a 1996 M1097R1, not A1. No, after tearing everything apart, there is NO pressure control valve anywhere. Chasing my tail thinking I'm following the manual only to find out the hard way that although referenced in the manual, it's simply not on this vehicle. Now I'm back to the beginning trying to figure out why it's not shifting correctly. No metal shavings, no burned out smell, fluid is clean. Just do not know other than replacing the entire transmission. Very frustrating.

The M1097R1 trucks are rebuilt trucks that started as other models, and can be either A1 or A2 series trucks before the rebuild. All that really matters is if it has a 3 speed transmission, you treat it like an M1097A1 for parts and repairs, and if it has a 4 speed transmission you treat it like the M1097A2 for parts and repairs.

 

[Chad Lares]

The M1097R1 trucks are rebuilt trucks that started as other models, and can be either A1 or A2 series trucks before the rebuild. All that really matters is if it has a 3 speed transmission, you treat it like an M1097A1 for parts and repairs, and if it has a 4 speed transmission you treat it like the M1097A2 for parts and repairs.

Well, no dice on the transmission. I put it back together, made sure that the fluid levels and everything is correct but it just barely crawls along. Pulling the transmission starting tomorrow. I'll see if the plates look burned up. If they don't, then I'm ordering a new one from Eastern Surplus. They have 3 speed transmissions listed for $595. It will cost $640 for shipping to Arizona but I don't see anyone else out west listing them. On the plus side, the engine actually runs good now. It was rough when I first started it but I think it sat for a while. One of the guys on here said he had the same thing and eventually, his cleared up and ran smooth so I'm still counting myself lucky... Once I get the thing moving...

 

[Mogman]

Well, no dice on the transmission. I put it back together, made sure that the fluid levels and everything is correct but it just barely crawls along. Pulling the transmission starting tomorrow. I'll see if the plates look burned up. If they don't, then I'm ordering a new one from Eastern Surplus. They have 3 speed transmissions listed for $595. It will cost $640 for shipping to Arizona but I don't see anyone else out west listing them. On the plus side, the engine actually runs good now. It was rough when I first started it but I think it sat for a while. One of the guys on here said he had the same thing and eventually, his cleared up and ran smooth so I'm still counting myself lucky... Once I get the thing moving...

Any decent transmission shop can rebuild the TH400.
Besides "used take out, not tested AS IS" does not sound too promising.
If you get it built locally any problems can be handled locally.