I have had the same problem with my F-250 2002, extended cab (which has a two part drive shaft) for as long as I have owned the vehicle. The problem is "catching" of the slip yoke splines of the drive shaft. After lubrication, the problem may resolve "permanently", but for me it only lasts a period of months and needs re-lubrication.
The fix is easy: Dropping the rear part of the shaft and pulling it out of the splined tube (mark everything and have the ebrake on so that you can get all back together exactly the same). Teflon lubricant is sold at Ford.
Details of this fix can be found elsewhere at this forum.

Thanks for starting this thread.....
Now my truck is doing this...}>

Those splines are machined to tightly. I would hit the male spline with a hi speed drill with a wire wheel on it loaded with grinding compound and then lube it. I can't see any lube working for a long time with those clearances. Mine did it when new which is why I got a good deal on it and then went away in a week by itself.

Those splines are machined to tightly. I would hit the male spline with a hi speed drill with a wire wheel on it loaded with grinding compound and then lube it. I can't see any lube working for a long time with those clearances. Mine did it when new which is why I got a good deal on it and then went away in a week by itself.

Has anyone done this? I have an '03 F250 that I bought a week ago and it makes the same exact clunk..I'm confident that the lube will take care of the issue; just wondering if anyone else has used the wire wheel and grinding compound.

Probably not, it's just something I dreamed up. They made them like that to compensate for the slip joint hanging out side if the tailhousing instead of in and the hanging weights are part of that compromise.

Thanks, appreciate it. I've been enjoying the truck otherwise, like the power but hate the ride. It rides like a board compared to my Jeep or F150. Anything to do about it? Maybe new shocks? Have new 275/65 R16s on them, not sure what the pressure is. I traded up from an '06 Jeep Grand Cherokee that I loved to bits but needed more power to get over the passes between here (Portland, Or. area) and southern Az. I have a 23' Jayco ultralight (19' box) that weighs 5k loaded, and I felt the 4.7 was straining too much in 2nd gear @40mph and 3500rpm when the grade was above 6%.:( The F250 V10 should yank it along like a dog with a chew toy.:-X04 On another note, we've been looking at 5Rs and am wondering how much different (better?) a 5R is to pull than my TT. I'm thinking of a 28' with about 9k loaded weight. I looked at a 35' triple slide with 10k dry weight yesterday and felt intimidated by the sheer size of it. Had a 19.5 5R many years ago that I pulled with a Dakota but that was a different animal. Any thoughts would be appreciated. If I don't get any replies on this old thread I'll try reposting it on a new thread if I can figure out how to make it happen (newbie, steep learning curve).