M939 transfer case air lines installed wrong

[05blackduramax]

Does any one have pics of the air lines routed the right way?

 

[jwesley74]

Does any one have pics of the air lines routed the right way?

Sorry, don't have pic but I just found our M923a2 was backwards too. looking at the auto engage switch the line running forward should be on right and the line that loops back to transfer case should be on left. It was easy to test, the full time air line hooked up left. The air switch from dash hooked up on right, and we tested by throwing switch on dash and air came out. Once it was connected we tested in mud. Our auto engage seems to not work at all, which is fine, I was going to take the washer off anyway. I'd rather beable to engage manually on the dash in Hi or Low range.

By the way, 2 out of 4 trucks so far have had issues with air lock out solenoid on transfer case. Couldn't shift in low-hi range when air pressure was built up. 1st truck was power supply, couldn't locate why no power so ran switched power direct to solenoid. 2nd truck same problem then we found inline mini-fuse under dash blown. Changed fuse, problem solved. Now I know what was wrong with first truck, but never located the fuse.

Hope that helps.

 

[trukhead]

Truth is, you almost never need to use the low gear. It is only for pulling something very heavy that is stuck. Such as a stuck forklift or some such. It is not really for any kind of driving. Just do not use low gear and you will not accidentally reverse in low gear.

On farm, I like to use low range almost exclusively. I think the transmission is better served going through the ranges up to 5th gear often rather than relying on first and second gear for the speeds I use the truck at primarily.

 

[05blackduramax]

So if the air line runs from the bottom piston on the back of the t-case to the front of the t-case were the valve/linkage is iam good to go? Thanks!

 

[lavarok]

post removed for a revisit on plumbing

 

[Suprman]

I can feel a slight difference in the steering wheel feel on-road with the front axle engaged compared to it disengaged. Both of my trucks are like this. Maybe it's because I am used to the way the trucks drive. I would think experienced drivers in a military unit would pick up on the same feeling when driving these trucks especially if the effect is enough to feel and visually see with premature front tire wear.

 

[lavarok]

edit : pics wont help. visual identify the letter on valve ports, see next post.

 

[lavarok]

On the subject of crossed air lines relating to the transfer case high/low dump solenoid: I had some time to spend under my two M923a2s today. When you visually inspect the interlock solenoid on the top of the transfer case, make sure you pay special attention to the letters next to each valve port.

The solenoid being used for this application normally has port C connected to port B, and port A is the vent which is activated when the solenoid is energized (A-B). The TM and all diagrams indicate port A is on the left (same side as wires) when looking forward from behind the transfer case and port B is on the right side and port C is on the end.

I can confirm this is NOT always the case. On one of my trucks, port B is on the left side!!! Both trucks were plumbed correctly when I received them. When I read this thread last week and visually inspected my trucks, I thought one was backwards and switched it. Afterwards, I would hear constant venting in the intake and my air dryer stopped coming on every few minutes. I then researched the solenoid on the Versa website and found the port diagrams and operational spec of the valve. You can too if you look up models starting with ESM-3302.

C = supply
B = transfer case
A = Vent

I switched the lines back on the truck and all is well once again. There was never a problem with either trucks plumbing in regards to this solenoid.

 

[wheelspinner]

Edited for stupidity.......I rechecked AGAIN, and they WERE backwards. All is better now. Really appreciate this thread....

 

[slapshot61]

incredible, who screws up the plumbing like this??

 

[Bolkbich]

I bought another m931a2. The air lines to the Tcase were wrong. I wonder how many trucks are running up and down the roads locked in 6x6....crazy

 

[plode]

I confirmed today that the front axle is locked on my truck. The auto engage switch with the wheel that normally hits the washer has zero effect when I move it by hand.

Can I just connect the front axle engage air line from the cab switch direct to the front axle cylinder on the back of the t-case, and plug off the air line from the PPV(and get rid of the wheeled switch entirely)?

I edited the picture below to illustrate what I'm asking.

 

[camoyj7]

I'm pretty sure you can just pull off the big washer that hits the switch.

 

[plode]

I already did that. I want to get rid of the switch entirely. Regardless of where the switch is(the roller part), air is still flowing to the front axle engagement cylinder on the back of the t-case. The switch moves freely by hand- and it does not return to the rearward position(high gear position if the washer was still there) on its own- it would stay in the low gear position if the washer was there. Instead of playing the move the airlines to different ports game and hope it works, why not just get rid of the switch entirely? There's no real point in keeping it.
I'm a person who likes things being simple.

 

[jwesley74]

I already did that. I want to get rid of the switch entirely. Regardless of where the switch is(the roller part), air is still flowing to the front axle engagement cylinder on the back of the t-case. The switch moves freely by hand- and it does not return to the rearward position(high gear position if the washer was still there) on its own- it would stay in the low gear position if the washer was there. Instead of playing the move the airlines to different ports game and hope it works, why not just get rid of the switch entirely? There's no real point in keeping it.
I'm a person who likes things being simple.

Ours is having same problem. Yes you can bypass the switch. Just pull off the line going to the T-case and line coming from dash air lever and connect together with fitting. Also recommend capping 3rd line going to roller switch as this is air pressure all the time for the auto engage. Our auto switch was failing and allowing air all the time to the t-case keeping locked in 6x6. We're bypassing it on both our trucks as we want manual control of when it's locked in 6x6.

 

[plode]

Ours is having same problem. Yes you can bypass the switch. Just pull off the line going to the T-case and line coming from dash air lever and connect together with fitting. Also recommend capping 3rd line going to roller switch as this is air pressure all the time for the auto engage. Our auto switch was failing and allowing air all the time to the t-case keeping locked in 6x6. We're bypassing it on both our trucks as we want manual control of when it's locked in 6x6.

I'm going to go out and do this today...as soon as the ground under the truck dries. I power washed the bed about an hour ago. Will post back if it works. I'm sure she'll be happy to get that front axle unlocked.

 

[plode]

Just finished up connecting the in cab switch direct to the front drive actuator and plugged off the feed line from the PPV. Works great now.

 

[74M35A2]

I don't believe mine to be correct on my M925A2. Though I have not actually looked yet, when I have the transmission in neutral, and I depress the transfer case shift lever button (still in T-case Hi range), the truck softly jumps forward about 4 inches, and I can repeat this. The transfer case lever is difficult to move into N and Lo. When in Lo, the front axle lock light does not come on. The front axle engagement and light do work correctly in transfer case Hi range, as confirmed via this winter's MI snow banks. I do need to study and compare the air schematic vs what I really have. In lieu of that, if anybody experienced the same situation, please advise. Thanks.

 

[Scott88M]

If it helps anyone, the problem my truck had was someone at some point put the low transfer front drive washer on the wrong side of the little air actuator. So it was stuck on. I just unscrewed actuator and shifted it down so washer wont touch it at all and screwed it back in. I don't want front wheel drive when in low transfer unless "I" lock it in.

 

[Andyrv6av8r]

I just removed the arm off of the air switch/valve on both of my trucks. Much easier than fooling with the washer.