To check your u-joints take off your drive shaft and move the yolks on each end with your hand. See if they are move smooth or feel stiff like they are dry and binding. They may looks good by looks can be deceiving.
Good advice...I KNOW they are not loose because they don't clunk when I reverse so they might be tight/rusty. I'll have to wait for better weather now - we just got 18" of snoa last night. I really love this truck! 4wd rules!