I thought is was the front drive shaft so I took it and had a new spline installed, balanced and new front u-joint (Spicer). He checked out the CV u-joints and said they were fine. Went to the hunting cabin this weekend and my thumping sound is still there when I climb or descend hills in 4 Hi or 4 Low. Ideas? First thing I'll check is the Warn Hubs and make sure something didn't tear up in the hub. It's hard to drive the truck and look underneath at the same time and noises travel.