My son inlaw went into 4 wheel low drove 50' in snow, heard some grinding, then all 4 wheels locked up, thus skiding to a stop, wheels would not turn. There is nothing in 4 wheel high, the engine revs, but truck doesnt move, in 2 wheel drive every thing works, truck is at the dealers taking a christmas break (pun intended), but their so called 2 hour diagnostic didnt reveal anything.

any thoughts as to the problem???

And a merry Christmas to all.

Sounds like maybe the transfer case piled up.

Is it a Electronic Shift or Manual Shift ?????

Tranfer case or front diff siezed. I suspect the front diff. If you reach under the truck in 2 Hi does the front shaft turn freely?

Fingers is probably right. I didn't see the part that says everything works find in 2wd.

I don't think the front diff because some stuff still turns up there even in 2wd. I think it's the t-case.

Only the half shafts turn in 2 Hi, the carrier is disconnected.

Only the half shafts turn in 2 Hi, the carrier is disconnected. Spider gears spin because the ring is stationary and one side gear is turning.

True, but carrier does not. I'm thinking broken pinion or ring gear.

New Venture Transfer cases tend to fail by breaking the chain. When they do, the front usually locks up when the chain spools off the upper sprocket and around the lower sprocket. Almost always breaking the case in the process. That could still be the case here. I am keying off the all four wheels being locked up.

SOunds right

Too bad it's in the shop. Dealer should have a least pulled the front shaft. Later! Frank

Thanks for the replies.

I will follow up with the dealers reply, Tuesday or wednesday

Can't drive around with a front shaft out of these like the old days, there is a slip yoke on the front shaft too, remove the shaft and there is nothing to keep the t-case fluid in.

Well it turns out to be the front differential, they are in the process of deciding what has to be replaced, will report final damages when the truck is returned.

drive safe.

The front axil is being replaced, no word as to what happened inside the differential.

Thanks and drive safe.

Would be interested in what went bang.

Truck returned Thursday, the work order stated that the differential pinion was siezed that the bearings were frozen and all bearing surfaces scored (6000 miles on truck), the oil level was normal and no signs of oil leaks, this truck was maintained by only one dealer, I think some one forgot to put oil in the differential.

The dealers in the Toronto area and most of Southern Ontario have pickups that visit GM parts depot twice a day, and a one day delivery from Michigan (at least that is where the diff. was supposed to come from).

drive safe.

Sure sounds like no oil. Only other thing would have been improperly set up pinion bearing preload. Glad to hear it's getting fixed.