Ford Repair: 03 Ford Exp XLT 4.0L V6, 63K miles, car shutter, ford exp

Question
Our 2003 Ford Explorer has difficulty on accelaration or up steep hills.  It makes the car "shutter" or "hop" and we have to back off of the gas to let it get back down to around 50 mph so it catches up with itself.  If it is pushed too fast it starts up again.  This is a serious problem, because it can't get out of its own way.  The Ford dealer lost our trust on a previous issue and we are afraid to take it in and get ripped off.  We aren't sure if it is a cam issue or possibly a transmission issue.  This is getting progressively worse.  When we took the car in to have the tires rotated the dealer told us there was a problem with an oversensitive 4WD and because our tires were uneven (newer on front) we would feel it.  The tires cannot be rotated because it grinds and feels like it is stuck in 4WD.  We have not had any work done to the transmission, as far as servicing, because the manual said to wait until 100K miles.  We are hoping you can point us in the right direction.

Answer
well the oil should be changed at 30k if u wait tell 100k the trans will not make it   , alot of problems with those trans..... the dealer is telling the truth on the tire issue , the tires and not vary more then a 1/4 inch other wise the transfer case will shudder , anda lot of places are putting the wrong transfer case oil merc 3 only , i would  get the trans and transfer case oil changed , and also check and make sure that the tires are not more then a 1/4 inch in difference and same brand