I've got an '05 Ford F150 4.6L V8 SuperCrew XLT 2WD. When I'm at a stop, truck is running (idling) in D (Drive), and I let off the brakes, truck starts to roll like every vehicle with an automatic trans does, just as soon as I push the gas and the truck starts to accelerate, there is about a half of a second delay before I feel, and barely hear, a clunk under the truck, almost like something is sliding back then hits something and stops. I was told by one person it may be a loose trans mount. Now accepting any and all suggestions and ideas, and any of either are much appreciated. Thanks guys (and gals).

 

Slip yoke on the drive shaft.

 

Ditto. Slip yoke thump. Its common and the only long term fix is replacement, at least in my experience.

 

Do our trucks use a 2 piece unit? if so has anyone drilled/tap a zerk fitting to make things easier in the future?

 

Great! I was thinking it was the u joints but I'll take that shaft apart and grease it. Does it have to be Ford grease or will any grease work on this. I noticed he mentioned teflon based grease. Is this a "must"?

 

FEI (For Everyone's Information), I dropped the drive line, cleaned out the slip yolk with carb cleaner, greased it up, and reinstalled. It's like it was never clunking. Almost as good as new. Thanks to everyone.

 

^ I would assume any heavy grease would work

 

I assumed the same thing and got what I could. A heavy duty general propose grease. I dropped the whole drive shaft (because it's two-piece [there's a joint in the middle]), deburred all the spline teeth in the slip yolk, cleaned it out with carb cleaner, put a pretty good bit of grease on the inside and a good coat on the outside of the slip yolk, reinstalled, and it works damn near as good as new. If any of the teeth in the yolk are chipped, bent or cracked, I would suggest a new yolk, or just a whole new driveshaft (I'm not sure if the yolk is capable of being R&R).