You will need to find the weight of your vehicle listed on your driver's door jam.
1)Add to that weight what your and any passenger weight plus any other weight you put inside the vehicle.
2)Subtract that total from the 8,400 lbs. combined weight (GCWR). That figure will give you the total weight that you can tow, i.e. maximum weight a TT can weigh with all the personal items and supplies. loaded.
EXAMPLE: Your maximum weight going down the road cannot be over 8,400 lbs. If your vehicle weighs 3,500 lbs. and you add 200 lbs. to it you would subtract 3,700 pound from the 8,400 leaving 4,700 lbs. Now if your TT weighs 3,500 lbs. and you add 400 lbs. into it you would have 3,900 lbs. leaving 800 lbs. for additional cargo before the total GCWR was maxed out.