gdafoe

Spent some time camping in the woods this week. Shifted into 4wd one time going through a mud hole with the 5th Wheel camper. No problem until I got out to the hard surfaced road. Got to the gravel shoulder and shifted in and out of 4wd several times. The lights indicate that it is not in 4wd but the rear end is locked up. This is an 08 3500 dually with 4wd. Any help would be appreciated, Thanks.

jhenson

Sounds fishy to me. You sure it's the rear end and not the t-case locked between gears??

rockcrawler304

Sounds like t-case issue. The rear would have to have something break to lock it up.

gdafoe

Well, guys that is why I asked because it seems real strange to me as well. I'm not at all convinced that it has anything to do with 4wd system. What I do know is that the rear axle is acting like as if it is totally locked, (no differential). What I don't know is when it started. It seems I should have noticed it when I first pulled out of the dirt onto the hard surface. But it did not become evident until about 100 miles later. So something may have broken it that 100 miles?? I did get it home. Today I am unhooking the 5th wheel, and I think I will jack the rear end up to see if releasing all pressure with do anything for it. Does this rear end actually have a locking mechanism or is it just the abs brake system that does the anti spin or what ever dodge calls it? If is it the T case that would lock the front and back together, right? It does not seem to be sliding the front at all. This is a heavy rig at about 25K lbs truck and trailer so there is a lot of weight on the rear end.

gdafoe

Ok so latest report is this. Unhitched the 5th wheel, drove it in circles on dirt, shifted into 4wd, spun the wheels fwd and reverse, jacked the rear end, shifted 4wd in and out, spun the wheels fwd and reverse off the ground. The differential is locked up. Something must be broke, any ideas as to what?? I'm stumped. It drives straight fine with no strange noises, but try to turn on hard surface if you go very far will snap or pop like your breaking a gear tooth off or a release mechanism is releasing with a snap. Next thing appears to be to take the diff cover off and take a look. This is not a daily driver, used mostly to pull the RV trailer and occasionally an equipment trailer.

jswar

Its my understanding that our trucks have AM General differentials and that the limited slip does not use a clutch pack like the older Dana style did.
If it were mine I think that I'd get it up in the air, drain the fluid, remove the diff cover and take a look. You should be able to turn an axle and watch the gears move.

rockcrawler304

Right now it's a guessing game. You will need to pull the cover and inspect it. Drain the fluid into a CLEAN pan and run a magnet through the oil. Get a few cans of brake cleaner and spray the diff out nice and clean.
Doing what you describe there should be some obvious damage.