M939 transfer case air lines installed wrong

[99nouns]

Wes would know better but I am pretty sure buzzer has nothing to do with Hi-Lo gears, maybe the parking brake's sensor is broken ��, and when disengaged it still thinks it is still engaged. Does the truck �� move forward and back freely when parking brake is disengaged?

 

[l3oss]

I got the truck in my possession now. I have since discovered the High/Low leaver is stuck in HIGH. I’m unable to pull it up off the floor. Yes I’ve held in the button on the end of the lever when trying to do so. I thought this might be another clue as to what the issue might be.

Some irrelevant info... when I went to look at the truck before buying I took it for a test drive. Every thing seemed to be good on the drive, aside from listening o the buzzer. He said it’s had the flasher and buzzer for quite awhile and that it didn’t affect the performance of the truck. I want to try low range but wanted to wait till we were back in his farm yard to do so. Once back in his yard we got distracted buy a visitor arriving to see him. I got distracted and it’s no one’s fault but my own for not checking it. Ha ... whatever the issue is, it will be resolved.

All and any suggestions are greatly appreciated.
Thank you

Wes would know better but I am pretty sure buzzer has nothing to do with Hi-Lo gears, maybe the parking brake's sensor is broken ��, and when disengaged it still thinks it is still engaged. Does the truck �� move forward and back freely when parking brake is disengaged?

 

[simp5782]

I got the truck in my possession now. I have since discovered the High/Low leaver is stuck in HIGH. I’m unable to pull it up off the floor. Yes I’ve held in the button on the end of the lever when trying to do so. I thought this might be another clue as to what the issue might be.

Some irrelevant info... when I went to look at the truck before buying I took it for a test drive. Every thing seemed to be good on the drive, aside from listening o the buzzer. He said it’s had the flasher and buzzer for quite awhile and that it didn’t affect the performance of the truck. I want to try low range but wanted to wait till we were back in his farm yard to do so. Once back in his yard we got distracted buy a visitor arriving to see him. I got distracted and it’s no one’s fault but my own for not checking it. Ha ... whatever the issue is, it will be resolved.

All and any suggestions are greatly appreciated.
Thank you

Let all the air out of the truck and try to shift it. More than likely the interlock solenoid is stuck. This allows pressure to be put on the shift fork rod to hold it in place. the button on the transfer case handle is suppose to cut off and vent air via the solenoid to let it shift smoothly. They often have issues. You can either air down to see if it shifts or do a single line modification as below

https://youtu.be/N7--6jxGDBM

 

[l3oss]

Yes I did as you suggested. I went out to the truck the following morning once it had no air in the system. You were right... the T-case High/Low Handel operates as it should without air in the system. What would be the proper by the book fix to resolve this issue?

Is it 100% now proven to be a failed “interlock solenoid”?
- if yes can it be removed, cleaned, and then re-installed or would it be best to find one new in box?

Thanks for sharing your knowledge & tips

 

[simp5782]

Yes I did as you suggested. I went out to the truck the following morning once it had no air in the system. You were right... the T-case High/Low Handel operates as it should without air in the system. What would be the proper by the book fix to resolve this issue?

Is it 100% now proven to be a failed “interlock solenoid”?
- if yes can it be removed, cleaned, and then re-installed or would it be best to find one new in box?

Thanks for sharing your knowledge & tips

Just delete it like in the video. The solenoid isnt cheap nor reliable. Even a new one will crap out. It's on the pressure protection side and its the first thing after the wet tank so it gets gummed and rust crap with any water in the system. It was designed so soldiers didnt kick the transfer case shifter out of high range.

 

[99nouns]

I hope you drain those air tanks at the end of the day after everyday you drive it right? >:/

 

[simp5782]

Why I put auto drains on mine. It doesnt forget to drain the water every time the air dryer purges.

 

[l3oss]

What is the “linear valve” he speaks of in the video?

 

[simp5782]

What is the “linear valve” he speaks of in the video?

The valve in front of the transfer case. Has a big round washer behind its arm. Has 3 air lines going to it right there that you are going to re plumb. Looks like the valve on your parking brake. It's a linear valve or called a low range 6x6 Engagement valve. Its job is to automatically put it in 6x6 if you put it in low range which is not always needed.

 

[l3oss]

I’m likely making this more complicated for myself then I need to but in the video you gave me above .... I get confused from @ :50 - 1:00 ... where he’s talking about the 4 way block valve. From that one line goes to the “linear valve”(which is being deleted), and another line goes to the “interlock solenoid”.

Its been my assumption that this far that the “linear valve is the interlock solenoid”. Can you clarify this for me plz

 

[simp5782]

Interlock solenoid is round on top of the transfer case. Its round. The lunar valve is square. 2 screws hold it on. It's got a little roller on the end where the washer is.


The 4 way block the top line goes to the interlock on top of the transfer case. Take that line off that block. The bottom line on the 4 way block goes to the linear valve as its supply air. When you remove it from the linear valve run it back to the top fitting so basically hooking the line kn the bottom of the block to the top of the same block

 

[Buffalobwana]

Let all the air out of the truck and try to shift it. More than likely the interlock solenoid is stuck. This allows pressure to be put on the shift fork rod to hold it in place. the button on the transfer case handle is suppose to cut off and vent air via the solenoid to let it shift smoothly. They often have issues. You can either air down to see if it shifts or do a single line modification as below

https://youtu.be/N7--6jxGDBM

Wes, thanks for the video. Very helpful.

I have a question though. In the video, you have 5 lines that are removed. 3 removed from the linear valve and two supply lines removed from the block. (I think)

The 2 lines you mentioned will get spliced together, got it.

Im using the one supply line for an air-ride seat. That leaves one open port on the block and another line (pictured) that I don’t know what to do with. Cap it? I don’t see where you mentioned it.



Thanks again. That was very helpful.

 

[simp5782]

Wes, thanks for the video. Very helpful.

I have a question though. In the video, you have 5 lines that are removed. 3 removed from the linear valve and two supply lines removed from the block. (I think)

The 2 lines you mentioned will get spliced together, got it.

Im using the one supply line for an air-ride seat. That leaves one open port on the block and another line (pictured) that I don’t know what to do with. Cap it? I don’t see where you mentioned it.

View attachment 768681

Thanks again. That was very helpful.

That is the interlock solenoid air supply. Since you delete the valve just tie the airline up somewhere or delete the valve and all its lines if you want.

 

[Buffalobwana]

Thanks Wes