It should but I am not 100%

 

On a 4x4, the one-piece drive shaft's slip yoke goes into the splined output shaft of the transfer case, which is filled with Motorcraft Transfer Case Fluid. Some may run out the back when you pull the yoke out. I had just a bit run out when I did mine. That grease may get into that fluid. I plan on changing mine soon. I'm supposed to change it at 60K miles anyway, due to all the towing I do.

 

Gotcha. Figured it would be sealed?

 

The fluid does flow around/nearby the 2 shafts inside there, but it's not flowing thru or directly onto them. The shafts are up pretty high, so most of the fluid is probably in the sump most of the time. Hence, the grease solves the problem.

 

GM has the same clunk. Those guys use Teflon grease or get tell nickel plated drive shaft. Lucky I've never had the bump in my ford. My GMC did it a lot.

 

Do we know if there is a different part number for the nickel plated shaft?

 

In looking at the slip yoke part of the axle that really the part to narrow the focus. im going to try to figure out if it comes off and can be replaced.

 

The "Clunk" is also a bump, when you come to a stop and the rear suspension unloads (back end comes up), when the vehicle settles (back end drops back down to level) you feel a bump/clunk, almost like someone bumped into the back of the truck, what causes it is the rear slip-yolk on the drive shaft binds up and then when enough weight gets on it(when the truck settles/back end comes down) the yolk unbinds and "Clunk/Bump"

The distance between the rear axle yolk and the rear output shaft on the transmission or transfer case changes as the suspension travels, hence the need for the slip joint.

 

You can certainly replace it. You'd just dismantle the U-joint, pull the old yoke, and replace it with a new one.

 

Im going to see if ford sells the part and compare it to the original one I have in the mean time I found a little passage about the mechanics of the bump.

When you accelerate, the leaf springs flex, and this lets the rear axle walk forward slightly, which in turn moves the drive shaft slightly forward, and when you level out your speed, it goes back to it's normal position. Same thing when you back up, but in the opposite direction.

The problem is made worse if there are any blocks between the axle & springs, as it gives the torque even more leverage to move the suspension with.