Stuck in LA, 939 Locked in 6-wheel Drive - Ideas?

[railroadmike]

Help!! stuck in LA, have been down here to retrieve my M921a2, had a starting issue that is a mystery and so far solved, installed mud flaps, got insurance, temporarily worked out lighting, went to head north and during pre trip inspection realized the truck is locked in 6x6 mode, when aired up I noticed it engaged and cannot dis engage, shut the truck off and bled it and it releases, been reading the thread on mis plumbed trucks but no help, I can barely reach the valves on top of transfer case and I cant find a proper diagram to save my life, the mis plumbed thread is of little help as I cant see where it is wrong. I've been here days longer than I wanted and money is getting blown. Any one in LA that has had this issue and can help?

Mike 775-830-3042

 

[railroadmike]

931a2...

 

[Ferroequinologist]

Take the line off the switch on the dash to the right of the steering collum and plug both the line coming off and the port on the switch.

 

[railroadmike]

my switch is on the left, Same procedure? I have been going over this for a while, I am going to remove the auto select valve, but I dont know what is wrong from that point on, is the main air from the fitting on the frame near by, and the is switch air the big line in the bundle going forward?

 

[NDT]

Remove driveshaft?

 

[railroadmike]

ive been considering that, but the transfer case will still be locked, I have to fix this one way or another, may as well try to do it right

 

[Matt1970M35A]

You said this is costing you extra money and time you dont have.
Id do as NDT posted and be on my home were I could then take as long as I wanted to fix it and reed over the TM's in the comfort of my easy chair.

 

[railroadmike]

I have a shop, tools and friends here, I just need some one to explain the air, in a from this to this fashion, so far I've got from mounted frame air tee to B on the auto selector, large air line from cab to C, A to some where back and I need to know if this should go to the rear piston, or to the splitter on top, and then to the lock piston on top, and to the release solenoid, and the rear piston. I wish I knew where my TM is as its no longer in the truck.

I see a lot of posting on this topic I was hoping a knowledgeable person could call and walk me through it, the descriptions have been of little help as this is my first 939 truck, its not like any thing else Ive worked with, truck or locomotive, ill figure it out eventually, Im stuck for tonight to get plumbing parts to try what Ferro---- said to do.

I have started the truck, partially aired it up no engagement and the solenoid worked as I could hear the air release, and the lever moved, but when I ran it up to 100 psi and with the help of friends cycle in and out of gear the axle locked in, the cab switch seems to act fine as the light comes on and off, chocked in transfer case neutral I went to the back and moved the drive line and the front moved.

Shut the truck off, bled down the air most of the way no more solenoid click or air release with truck power on.

 

[gimpyrobb]

Who cares if its in 6x6 mode, just drive it home. Can you pull the spline caps on the front axle? That would eliminate 6x6 mode.

 

[railroadmike]

I have heard of major transfer case failures, and I am from the never on pavement school of 4x4 as it wrecks transfer cases, especially at freeway speed

 

[railroadmike]

I can pull many things off, I still want to know how to fix it right

 

[gimpyrobb]

That is wrong.

Especially if you pull the spline caps from the front axle.

 

[railroadmike]

its 400 miles home as well, I do really appreciate any help any of you boys are giving me, Im giving it one more day and then its off to the land of military ignorance, there is way more know how down here

 

[railroadmike]

so its ok to run this full time in 6x6? Then why have a selector at all? Ive seen many trashed transfer cases from pick ups left in 4x4

 

[gimpyrobb]

400 miles is nothing, you too worried about it, (pull the caps) and hit the road.

 

[gimpyrobb]

The selector is so you don't scrub the tires as much and maybe fuel economy.

If the truck does not have lock out hubs on the front axle, everything is turning anyway!

 

[railroadmike]

yes everything is turning, Im aware of that, but most 4x4 are set up to track properly by having the front pull ever so slightly more than rear, I have read this in many tech manuals, there is a big difference between part time and full time 4x4, I have seen much damage from not knowing this, you can lock the hubs on any 4x4 and roll, it changes when the case is locked to the drive line power.

 

[railroadmike]

I have read in other threads on SS that as many as half of the 939 trucks are mis plumbed, and has been a cause of major transfer case failure, as they were found with the front locked in at the time of failure, I got a real nice truck, why not do it right.

 

[railroadmike]

I just read there is a 6% overdrive on the 5 ton front axle locked in, no wonder the cases were popping.

 

[Csm Davis]

I just read there is a 6% overdrive on the 5 ton front axle locked in, no wonder the cases were popping.

That is on the 809 series. Unscrew the air lines going to the switch that is under the cab and plug them off if you still have air going to the TC locking piston find the line that is putting air in to it and follow it back, you have the easiest truck to do this work on take the deck off so you can see and get to all the lines and if that is to much work quit whining and drop the drive shaft.