* Check the sticker: Look for the sticker on the driver's side doorjamb or the owner's manual. This sticker will list the maximum towing capacity for that particular vehicle.
* Consult the owner's manual: The owner's manual will also specify the towing capacity, as well as important information about towing safely.
Without knowing the specific year and engine of the Grand Caravan, any number I provide would be inaccurate and potentially dangerous.