drafalske

Truck is a 2001 2500, 6 speed, with 126000 miles. It's a rebuilt total that I've had for about a year. The only oddity to note about the truck is that the transfer case is a 241 from an older dodge truck (shift pattern is a little different), and it doesn't have the PTO that a HO truck should have. It worked fine/no issues until yesterday.
I don't use 4-wheel drive very often, but we just got our first real snow and noticed a nasty vibration when I engaged it.
It engages and disengages just fine, but vibrates badly; and gets even worse when I let off the throttle. It ONLY does this in 4-wheel drive. As soon as I shift back to 2H, the vibration stops.
This sounds like a textbook u-joint to me, I just wondered if there's anything else I should look at while I'm under there.
Thanks!
Dave

torquefan

No, I think you will find a bad u-joint on the front shaft, especially thinking about the double cardan joint. You might also want to give the transfer case a shake and make sure its mounting bolts are tight. Have a look at the fluids in the transfer case and the front differential just to make sure they aren't running dry. Seen that before and the first sign is often a weird vibration or noise.

Busboy

It probably is the front drive shaft ujoints but it could also be a bent drive shaft if the truck has been smashed.

drafalske

The truck was smashed good enough to total the truck, but the front shaft is definitely not bent. This problem just came up yesterday. Probably been a couple months since I used 4-wheel drive... it was fine then.

Hodge

Any frozen material on the shaft, making an out of balance situation? Does it vibrate at low speeds? I would not use it until you find out what's going on. I just had my t-case replaced due to the front driveshaft coming loose and smashing a hole in the side of the case.

jcarrillo

Doesn't the driveshaft turn even when you are in 2 wheel drive with the full time hubs? Mine does. My Cardan joint went out the other day and I had to stop on the side of the road to pull it out before it trashed my transfer case. Does it vibrate all the time or just in 4 wheel?

drafalske

It vibrates at any speed, increasingly in severity as speed increases. Also worsens when I let off the throttle.
I'll check for frozen material on the shaft, but I'd find that unlikely. It's been below freezing here for several days. No snow on the way to work, a couple inches at lunchtime; thats when I noticed the problem. The snow is very "dry", but it made the roads slick. They've got them cleaned up pretty well now and I'm getting around fine in 2wd.
It ONLY vibrates in 4-wheel drive. 2-wheel is absolutely fine.

2001 still had the CAD, so the driveshaft does not turn in 2wd. That's only 02 models and up.

D

Purplezr2

Check the joint up on the transfer case, seen it a couple times where they are bad.

Mountaineer

check and make sure the bolts are tight that hold the shaft in place.
Trust me. It will cause a vibration when they loosen up.