whenever i am leaving from a stopped position my rear end just shudders like crazy..Happens all the time when leaving from a stopped position..I have to ease on the throttle to minimize the shudder..i was pulling my Camper the other day and the shudder was worse...Can anyone tell me what is going on with the rear end...i added the special Gear oil from Ford and it helped a little but not very much...i was told it was the clutch pack..when the rear end was opened,,they seen no signs of problems with anything in there,,and there was no clutch pack in my Rear Differential..Help would be greatly appreciated..

2004 Ford F150 Fx4 4x4...

 

It could be axle wrap a.k.a wheel hop. I'm not sure about the specs of you truck, but some trucks that are lifted and\or are putting down some serious power to the rear wheels will experience this. Mine, for example, is lifted and I installed traction bars in the rear to avoid this.

If you truck is stock and since it's newer, I would be surprised if it is axle wrap but you might take a look at your U-bolts, 3" blocks, and leaf springs. Could also be something with the drive shaft. Good luck.