I tow a fifth wheel, weighing 11k lbs. all the time and am having trouble with the front part of the driveline hanging up. It causes truck to stutter repeatedly. The truck will stutter at any speed when the problem occurs. 2004 one ton diesel, with 40k miles, bought used at 30k and had no problems until now. Ford dealer relubbed the front driveline splines with grease and that fixed problem for 400 miles or so. The pin weight coming down on the truck is about 2100 lbs. I will be bringing vehicle to a driveline shop this week. Any recommendations appreciated.