There are other options than crown wheel and pinion. Don't forget the very heavy duty vehicles of WWII the Pacifics used a chain drive to the rear axles. Also in use on Sentinel steam wagons until the 1950's. A chain is a very efficient method of transmitting power with little losses.
An entire transmission system is a chain of torque multipliers from the engine to the wheels. With few exceptions, every link, gearbox, transfer box, differential, hub reductions increase the torque to the driven wheel. Each link induces some loss is power through friction. The size and reduction ratio of each link governs how strong the next link down the chain must be.