I don't want to kick a hornets nest on my second post on the forum, but as a long-time mechanic and someone who's been on the wrong end of improper towing, it not about what a vehicle can physically tow.
about what a vehicle can control
. A tow vehicle has to be heavy enough, have the proper suspension, and enough traction that it can maintain stable towing conditions. It also has to have the braking power to arrest the momentum of a towed load in the event of brake failure on the trailer. Typically, a vehicle intended for towing also has over-sized brakes
; additional cooling capacity for the engine, transmission and sometimes for the power steering as well.
Can you physically tow something heavier than a vehicles rated towing capacity? Certainly. But the engineers that determine the maximum towing capacity for a vehicle are taking many factors into account to come up with this number, including a significant safety margin to account for people improperly loading a trailer or adverse towing conditions.
I was stupid enough to tow a very overloaded 1963 Ford Fairlane on a car dolly with a 1974 Duster. When the Fairlane blew a rear tire on the freeway at 70mph, my wife and I nearly died. Not an experience I care to repeat. We endangered not only our lives, but those of everyone on the road around and behind us. It shouldn't have taken such a drastic mishap to lear this lesson, but learn it I have.
proper way to tow a load heavier than your vehicle is rated to tow is to buy, borrow, or rent a heavier vehicle. Period.