I have a 2003 F150 (FX4) with 66,000 miles on it that has been shuddering/vibrating when I make sharp turns. I was pulling my boat the other day and the vibration got worse with the added weight. Does anyone know what the problem could be? My buddy said it could be the U-joint on the driveshaft going bad. I am going to take it to the dealer but wanted some guidance on possible scenarios before I went to battle with them! Any help would be greatly appreciated.

 

Clutch packs in the posi unit of the rear axle. Have replaced about a hundred or so over the last three years. You can try just adding a bottle of friction modifier to the axle before you take it in and see if it helps. Less than ten bucks and about five minutes of work.