Transfer Case Locked Up

The other day I was accelerating up a hill in third gear and as I shifted into 4th the 2 rear axles stopped turning. The truck would move forward or backwards a few feet, but something internally jams and it stops. I put the transmission and transfer case in neutral and the engine runs fine. With the transmission in gear the engine and transmission seems to run fine also, but if I put the transfer case in gear it locks up.

I got a friend with a truck to come tow me. The truck would not roll more than a few feet in either direction before stopping. That was even with the transfer case in neutral. I pulled the axle shafts and towed it off the road to a safe area. I then pulled the long rear drive shaft from the transfer case. With the axle shafts in and the drive shaft removed the truck rolls freely.

The transfer case appears to shift correctly since when it is in neutral the transmission spins freely.

So it seems that somewhere on the output side of the transfer case something is locked up.

The truck is an M35A2 with the air-shift transfer case.

Anybody have an idea what happened?

First, I would look on the outside around the emergency brake drum and see if anything has wrapped around it.
If that is all clear, there is something broke inside.

Everything is clear around the emergency brake drum. I figure something is broken internally, but I don't know what. I thought someone might have had a similar issue and have a good idea of what is broken.

The big question is should I tear it apart and try to replace an individual piece or do I need to get another transfer case?

Is it a SPRAG transfer case?

wsucougarx said:

Is it a SPRAG transfer case?

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Junglemist said:

The truck is an M35A2 with the air-shift transfer case.

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Is it locked in both high and low range on the transfer case?

The transfer case output to the rear wheels will not turn in neutral or high/low ranges.

Check your air to the transfer case. It sounds like it is stuck between gears.

Blood_of_Tyrants said:

Check your air to the transfer case. It sounds like it is stuck between gears.

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Make sure there is air getting to which component? I was not aware that air-pressure affected anything other than the front air-shift assembly.

I may be wrong, but I think that the transfer case shifts the front axle in and out.

The transfer case powers both the front and rear wheels. Pressurized air is run to the air cylinder on the front output of the transfer case to engage/disengage the front drive shaft. I have the front-wheel drive lever in the "out" position so the front drive shaft spins freely. The rear axles are always powered.

The problem is that power from the transmission enters the transfer case and somewhere in the output (Past the control lever) something is not turning.

I have searched the posts on here, but have not seen one with this issue. The transfer case never slips out of gear like they do when the gears are worn, and it has not been giving any odd noises.

I thought air shift engaged only the front axle. If you pulled the rear driveshaft could you limp home with the front pulling? I had to do this on a jeep and a blazer when I lost the rear drive shaft. I just put the yoke back in and took it slow.

After Re reading I see that the transfer case may be fubar. I was still wondering if you tried running on just the front.

sounds like you stuck between high and low range, at least that was the case when it happen to me. after a breif panic and looking like wizard of oz pulling lever and such , I put in low range flip it in the front put it in reseve half throdel in pop back in and away I went. has not happen since. Maybe I got lucky but it worked mine was doing the same move 2ft each direction and lock up. by the way hows the amish down your way?

air shift is just for the front.i would look into the brakes both the e brake and the service brakes if a return spring breaks it can cause the brakes to lock up..i would check that first .

pull the drain plug on the t case just to get a little fluid out so you can check to see if there is alot of metal in the fluid. if so theres a good chance the t case is pooping out on you but i would look at the brakes first since that seems to be way more common

stampy said:

... If you pulled the rear driveshaft could you limp home with the front pulling? ....

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no - if the output shaft is bound up, the front will be bound up as well, because the front output is engaged to the same output shaft via gear set.

The brakes are fine. I towed the truck for about 8 miles with the drive shaft removed and the 2 rear axles roll freely. I checked the emergency brake and it is clear.

I did not attempt to use the front axle for the same reason that Mudguppy gave.

southdave said:

sounds like you stuck between high and low range, at least that was the case when it happen to me. after a breif panic and looking like wizard of oz pulling lever and such , I put in low range flip it in the front put it in reseve half throdel in pop back in and away I went. has not happen since. Maybe I got lucky but it worked mine was doing the same move 2ft each direction and lock up. by the way hows the amish down your way?

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I have not tried anything like that. I was afraid of really breaking something, but I guess if the transfer case is a total loss then it might not hurt. I am going to try to check for metal pieces in the fluid.

Down here the people call themselves Mennonite not Amish. They are all over the country in different communities. Some communities still use horse and buggy while Mennonites in other communities have started many of the countries biggest businesses.