Truck Repair: F150 slip bump, slip yoke, f150 2wd

Question
I have a 2004 F150 2wd with 5.4l 3.55LS. When I slowly accelerate from a complete stop there is a slight "bump" or slip or shudder that seems to come from the rear end. This is not real bad but it is irritating. There is not play that I can determine from trying to move the driveshaft. The truck has 22,000 miles and has been doing this since day one.

Answer
Slip bump is a good name for it.
What I have found is the splines in the slip yoke of the driveshaft have some friction as torque is applied, which resists sliding of the splines.
During takeoff, the rear axle rotates slightly, and actually moves foreward under the truck as it is pulling the truck foreward.
The resistance to slippage is finally overcome by power, or less resistance as the truck body moves, and the splines suddenly move, allowing the driveshaft to shorten.
Pulling the driveshaft slip yoke out, and liberally lubricating the splines will help. You may need to do it occasionally, when the bump comes back.

Van