About 2 months ago I had my rear pinion seal changed in my 06 S-crew 5.4 4x4 because of a leake only had 8000 mi. on at the time. Now within the last month or more I have been noticing a clunk or thunk noise what seems to be in the rear of drive shaft maybe. Only when I take off from a stop . sometimes one thunk sound, and other times 2 or 3 thunk sounds I am going to make an appointmen next week for it since it is still under warranty, but does anyone else had or have this problem? Does anyone Know what it may be other than REAL annoying. Don't like any noises other than the rumble of my motor and exhaust.

 

Might be the slip yoke needs lube.

 

How and where do I do that?

 

My guess would be that when they put the new seal in, they either didn't put it a new crush sleeve, or they put in a new crush sleeve and either tightened too much or too little. The clank you hear is the pinion gear and the ring gear slapping. But it could be a U-joint also.

 

The clunk you hear is more than likely th drive shaft moving to the rear when you accelerate. This is a known problem on some F150s of all vintages. My 1997 has done it since new. The "fix" is to remove the driveshaft clean out the female spline (front) of driveshaft. Reinstall the shaft after applying Teflon grease liberally in the drive shaft spline. There is a TSB on this problem and I just explained the fix that they suggest. It will not stop the problem forever. I have to remove, clean and reapply grease every 10,000 miles of so or just live with the noise. I don't think it has any effects on durability or premature wear of the components but it is anoying. Good luck.