When I let the clutch out the rear end seems to slip. when i turn the drive shaft the whole shaft turns not separately from the ujoint. U joint or something else? the truck has about 105 K

 

what do you mean it turns "not" separately? as in the drive shaft and u-joint both move the same with no play between the two parts? and what do you mean the rear seems to slip? the only thing that can "slip" is the clutch. everything else is a mechanical connection. if there was a problem it would be a banging grinding nothing happening situation