20065 F150 Extended Cab, 102,000 miles 4.6 2X4.This is going to be hard to explain, but when I'm at a complete stop and release the brake and give it some gas there is like a clunk or skip, multiple, and there are more clunks/skipping as it gets warmer, up to operating temp. The more you hit the gas the less of a problem exists. It's not an audible clunk but you can feel a slight clunk or skip. I know this sounds weird. It's kind of like there might be a few teeth missing on the ring gear and it's skipping through to get to the teeth that are still there, but the gears look good. No undue wear. It only happens when taking off from a stand still, or at least I don't notice it when I am rolling and let off the gas and hit the gas again. I've checked the motor mounts, spring perches, transmission mount and U-joints. Could it be the bearings on the pinion shaft? Rear brakes not releasing right away? If anyone has any idea what to check next

 

I see you say you checked your U-joints, but I would double check them. Sounds exactly like your problem.

 

Ive had the same problem since I bought mine used. I usually feel it when Im coasting through a parking lot. At first I thought it was the cracks in the concrete causing it, but it started happening everywhere. It doesnt happen everytime either, just occasionaly.

I told my mechanic and he said everything checked out ok. But I guess I need to crawl up under there and check for myself.

 

Finally got a good look at the U-joints. They're good. This only happens from a dead stop. If I slow down coming to a red light and it turns green before I completely stop it doesn't happen. I am totally baffled by this. Anyone else have any ideas?