Originally Posted by Scott91370

I'm going to say that even though the sand is soft the tires are not turning at the same speed. One or more tires are getting the grip and other(s) are spinning. Similar to trying to turn on dry pavement.

Originally Posted by marshallr

It sounds like the chain in the transfer case is stretched and is slipping when under load. That is what happens when you drive in 4X4 while on road surfaces with good traction. There are a lot of people who come on these forums and will tell you it is OK to drive in 4X4 on pavement. It is not. BTDT and paid the bill to have transfer case rebuilt.

The damage is cumulative and it doesn't break all at once. But parts wear out gradually. Often, as in your case, it is the next owner who gets to pay the bill.

You can see the internals here. When the driveline is under stress something has to give. Sometimes parts break, sometimes they stretch. Once the chain stretches it will start to slip over the cogs when under a load.

photo of transfer case - Bing images

Originally Posted by Wic33

Thanks for the reply. Why would transfer case chain not slip when I run in reverse in 4WD? As I mentioned, just to test truck out I ran in reverse on beach in 4WD for way longer than would ever need to and no issue at all. 4WD system worked perfectly in reverse.

Originally Posted by wilit

Probably because when it's used in drive the faces of the gear and chain mating surfaces wear out. Since you rarely drive in reverse, those surfaces don't wear out, so the chain doesn't slip.

Originally Posted by wilit

Probably because when it's used in drive the faces of the gear and chain mating surfaces wear out. Since you rarely drive in reverse, those surfaces don't wear out, so the chain doesn't slip.