It is never a good idea to tow more than a vehicle's stated towing capacity, which is referred to as a Gross Vehicle Weight Rating. A vehicle's frame, suspension system, engine and axles are designed to carry a maximum load. Many problems can result if the towing capacity is exceeded.
If the towing capacity of a vehicle is exceeded, tire failure may occur. The vehicle engine may also overheat, causing the drive train to be overloaded, effectively harming the transmission. In addition, with added weight on the rear of the vehicle, the brakes may lose effectiveness, taking much longer to slow down the vehicle. The driver may lose control of the vehicle. Both the immediate potential effects and the long-term vehicle wear and tear are reasons not to exceed towing capacity.