Have a 2006 f150 4x4 5.4L supercrew that has been in 3 different ford dealerships for 2 years trying to be fixed. When driving 50-55mph and I release the accelerator there is a jerking clunking sound/feeling coming from the middle to rear of the truck. Have had the rear end rebuilt, the transmission taken apart, checked, and rebuilt, was in brand new condition, u-joints replaced, new shocks struts, and still no one can figure out why. Does not do it at higher or lower speeds, and the level of severity changes, sometimes its a small bump feeling and sometimes it's so hard it feels like Ive been rear-ended. Does not do it when the accelerator is pressed, only when it is released, like if something was disengaging. Also does it with or without the overdrive on. Has anyone experienced this?

 

Grease the splines on the driveshaft and try that.

 

The shop should have use "ears" to ID the specific issue when the common fixes didn't work. Just purchase a set of these and you'll be able to ID the location of the sound in short order..