The slight leak isn't uncommon. Just make sure to check the differential fluid and keep it full. If it is only a couple drops per day, it will go down slowly, but keep an eye on it.
As far as checking the U-joints, park the truck, place the parking brake on, and place the transmission in neutral. Make sure the vehicle can't move because you need to get under it. Craw under the truck and check at each end of the drive shaft to locate the u-joints. Once located by hand wiggle the drive shaft back and forth / up and down to see if there is any play from the joint.
Let me know what you find, and make sure the truck can't move when you are under it.
Joe
Tuesday, July 20th, 2010 AT 12:25 AM