OK, first off, put down the owner's manual and go to the truck and open the Driver's door. There should be several labels/stickers on either the edge of the door or on the door pillar. Write down those numbers, especially the GVWR, GCWR, and GAWR Rear, there should also be numbers for the Max Cargo cap. Then do the same for the label/sticker on the front drivers side of the TT. With those numbers in hand, come back here and post them, then folks will be able to help you determine where your problem is.