I have a 99 4x4 F 150, When i stop anywhere,or anytime, as soon as i start to move again, i hear , and feel a bang coming from the back of the truck, it only does it sometimes, but doesnt matter if i been riding for a while or just starting out, but it only does it when i start moving again from a complete stop. I havent checked anything yet, but feels like its coming from the rear ???

 

sounds like the slip yoke, where the drive-shaft spline goes into the tranny. Ford sells a grease that solves that. i have the same thing in my '02(only a 2wd tho) and that seems to be the explanation. hopefully someone will either correct me or reinforce my theory...

sherm

 

It agree, it sounds like the slip yoke. With mine, it felt like the "thump" was right under me. The teflon grease will fix it. Mine took about 2 days of driving before it stopped, I guess the grease had to work itself in. The other possibility would be a U-joint.

 

Got it in my 97 from day one. The grease job lasts about 2-3,000 miles. Can't believe Ford would sell trucks for as long as they did with this defect. Will think before I buy another Ford because of this.