M936 A2 transfer case problem

[Jeepsinker]

So I put my transfer case in neutral today to engage the pto for the crane on my truck to test everything that runs off of the rear pto. Everything worked fine until I tried to put the truck back into gear. It wants to stay I low gear or neutral. The shift lever was bottoming out on the floor and still not putting it into high range, so I adjusted the linkages under the truck all the way out so the lever doesn't hit the floor when I push it down hard, but still no luck, and the air switch on the linkage won't go back to the drive position either. Going to mess with it more tomorrow. Transfer case was replaced in 2011 and no miles on it since except by me. Any suggestions for tomorrow?

 

[NDT]

Try getting the truck rolling in low range and then shift to high.

 

[ProPower]

Mine also got stuck when I first brought it home! A little penetrating oil on the shifting rods, some adjusting and now it works fine! I also pitched the low range/reverse safety lockout rod because it was binding up just like yours! Id start there! Good luck!

 

[Jeepsinker]

I did try rolling it and shifting with no luck. Drove all the way across the field while pushing down furiously on the shifter. The reverse safety lockout rod, is that the little air switch dealie with the roller on it that contacts a washer on the linkage?

 

[Jeepsinker]

Maybe having the front drive shaft in would help, I can't see why it would make a difference though.

 

[Scarecrow1]

If it has a button on it like mine did check it out with a volt meter to make sure it's getting power to it . Those wires under mine are a mess and I have scheduled a re wiring for that mess in the spring . My point being it may be the silanoid that's not working .

 

[Jeepsinker]

I will check that out. Where is the solenoid located at? I was able to get it back in gear today, just have to do it with the engine shut down.

 

[Scarecrow1]

The button on my 923a1 is located on the end of the lever so,as you can press it with your thumb as you pull up on it . Mine hung up like yours did the first tme I ever used it and brother it took me a while to get it back in . I never used it again lol , and hope I never do .....

 

[Jeepsinker]

Lol, I know where the button is man. Where is the solenoid you speak of? I haven't seen one under the truck.

 

[m16ty]

I disable the t-case shifter interlock on every M939 truck I get. It solves a bunch of shifting problems on these trucks. To find out if this is the problem, drain all the air tanks and see if the t-case will shift. If it does, the interlock is causing problems.

To disable the interlock, look on the top front of the t-case. You'll see the end of a cylinder sticking out of the t-case with a air line attached. remove the air line, plug the line, and plug the cylinder. You'll never have to worry about that button on the shifter again and the t-case will just shift better in general.

 

[Artisan]

I kinda remember reading here on SS that this is the way it was designed.

M16ty's suggestion seems valid.

If you do it please post your results!

 

[SLOrazorsedge]

I had the same issue with my M936A1 with the interlock button. In a pinch, pedal pump your brakes to bleed the air pressure down below 30 psi and you'll be able to shift the transfer case. It happened to us after using the crane out of the blue. I still haven't got to the route issue but M16ty does have a point on disabling the interlock...

 

[Trailboss]

I have had a couple of trucks you had to shut off and bleed air in order to shift into high. I've flipped the interlok roller on all my trucks, but I may just do the bypass described by m16ty.

 

[Jeepsinker]

Yeah that's my problem because it shifts fine with no air in the system. Have to go to the hardware store and get some pipe plugs now. Thanks Ty.

 

[Csm Davis]

Okay so I will play devils advocate here and say don't disable the shifter lock on a wrecker, other trucks sure, I know it is unlikely to happen but the wrecker is the main one that will be running with the transmission in gear and t/c in neutral and no one in the driver's seat, if it fell back into high it could be a disaster. Generally cleaning and lube will fix the hard shifting and some need wires or something fixed not really hard stuff, you could even put a air switch on the dash if you want to get rid of the problematic electric switch.
Now the interlock for all wheel drive should have never been put on the trucks in the first place.

 

[Jeepsinker]

Yeah I see your point, but I was fiddling with it last night and got it in drive high with pto still engaged and it wouldn't move out of its tracks without stalling until I disengaged the pto. I also set the air brakes and use wheel chicks between the tandems. However, if it is a simple wiring fix then that is what I'll do. It is raining outside right now so I'm not doing anything.

 

[SLOrazorsedge]

Jeff does have a valid point, I could just see running the wrecker crane or deck winch with the motor on the auto kick up 1600 rpm and the transfer case suddenly dropped into gear, either everyone gets killed from the shrapnel from the tranny and transfer-case exploding or the truck launches like the winning frog in a frog jumping contest....I think I'll climb back under and fix it right.

 

[M35A2-AZ]

When I got my truck I could not shift the truck in to low and getting it back into high was a pain.
I found that the shaft that the two shift arms ride on under the truck were loose and had a lot of play in them.

 

[m16ty]

Okay so I will play devils advocate here and say don't disable the shifter lock on a wrecker, other trucks sure, I know it is unlikely to happen but the wrecker is the main one that will be running with the transmission in gear and t/c in neutral and no one in the driver's seat, if it fell back into high it could be a disaster. Generally cleaning and lube will fix the hard shifting and some need wires or something fixed not really hard stuff, you could even put a air switch on the dash if you want to get rid of the problematic electric switch.
Now the interlock for all wheel drive should have never been put on the trucks in the first place.

I guess you do make a point on a wrecker. I'm still of the opinion that on something that doesn't use stationary t-case pto work, the interlock is still useless.

 

[Csm Davis]

Yeah I see your point, but I was fiddling with it last night and got it in drive high with pto still engaged and it wouldn't move out of its tracks without stalling until I disengaged the pto. I also set the air brakes and use wheel chicks between the tandems. However, if it is a simple wiring fix then that is what I'll do. It is raining outside right now so I'm not doing anything.

Yeah that's what is supposed to happen but I have one that will take off with pto engaged! So it could happen, but hopefully not. A lot of wreckers are sold missing parts and mine was missing a safety feature, the brake auto lock.