M931A1 Transfercase Issues

[fuzzytoaster]

This M931A1 has been giving me trouble and I fear the t-case is dead. Engaging any gear with it in high range results in a heavy steady grinding from the t-case and engaging it in low feel like it's locked up. I got lucky and manged to gently move the truck under its own power a few feet in low yesterday and I've been unable to replicate that. Putting the t-case in neutral and going through the gears shows the transmission is responding normally but when in low I can feel it engage and just sit, no amount of "foot to pedal" changes it. I've been digging through the forums and making sure that the electronics are clicking and engaging when going into low but am not sure if it's supposed to click when going into high range or not. The fluids are new and it is an RRAD truck (i know i know). The ABS light is on so one of my first thoughts was that the brakes could be locked up from sitting but that doesn't explain the grinding in high range and that fact I tow bared it home and used the brakes during transit. The ABS light is on due another simple issue entirely. Any input would be appreciated to save such a nice truck.

 

[Coffey1]

Just checking did you put t case and tranny in neutral before towing.

 

[fuzzytoaster]

Just checking did you put t case and tranny in neutral before towing.

Yes, made sure of it.

 

[Coffey1]

Have you checked to see for sure the spring brakes have released.
They will grind if not fully engaged.
Have you checked t case to make sure it has oil in it.That was the one fluid I forgot to check when I got my truck and it was almost bone dry.
Have you pulled drain plug on t case to see if grear's or parts of grear's come out or huge hunks on plug magnet.

 

[M35A2-AZ]

Sorry for your problem. Sounds like it maybe the transfer case.
Towing it with the drive shaft hooked up to the axles may of did it in.
I think I remember seeing something about when towing not to get over 35mph.
The transfer case has a oil pump in it and when in neutral it may not pump the oil right.

Does the shaft lever move freely?

I try to remove the drive shafts when I plan to tow one. But that is just my thinking and 2 cents.

 

[MuleMac01]

Check the oil if it's black and if the drain plug as chunks of metal think it might be done for..

 

[fuzzytoaster]

Have you checked to see for sure the spring brakes have released.
They will grind if not fully engaged.
Have you checked t case to make sure it has oil in it.That was the one fluid I forgot to check when I got my truck and it was almost bone dry.
Have you pulled drain plug on t case to see if grear's or parts of grear's come out or huge hunks on plug magnet.

Brakes are releasing but I wouldn't doubt if they stick a little. As for fluids I checked today and they are good, minor shavings on the plug but nothing notable.

Sorry for your problem. Sounds like it maybe the transfer case.
Towing it with the drive shaft hooked up to the axles may of did it in.
I think I remember seeing something about when towing not to get over 35mph.
The transfer case has a oil pump in it and when in neutral it may not pump the oil right.

Does the shaft lever move freely?

I try to remove the drive shafts when I plan to tow one. But that is just my thinking and 2 cents.

The shaft lever moved between all 3 positions but takes some effort crossing in between them, it's easily the "smoothest" of any of my other m939 trucks. I've had good success in towing trucks with everything in neutral but it very well is possible that did it.

Check the oil if it's black and if the drain plug as chunks of metal think it might be done for..

Fluid level was good as was the drain plug.

 

[fuzzytoaster]

I went out to play/inspect it again and she moved under her own power in low range; no unnatural noises or strain. I didn't want to waste the opportunity so I parked her on a gentle incline and shifted into high range and she took without the grinding. The lever was more ridged to move into high range but that was about it. I've not put her back into low range as I pushed things far enough for today. I feel as though the drivetrain may have been bound up in just the wrong way that it didn't want to function but we shall see.

 

[engineer233]

I would take the inspection plate off of the top and look down in it and watch the hi/lo shifter fork and make sure it is moving properly. Kinda sounds as if it may be hanging between gears. Just my thoughts

 

[Tow4]

My M929 transfer case shifts much easier if the truck is rolling. I have also had to put the transmission in gear and then back in neutral with the engine idling and the transfer case in neutral to spin the transfer case so I could shift it with the truck sitting still.