FORD calls its full-time, four-wheel drive system Control Trac. Unlike other systems which have a viscous coupling centre differential, the Explorer uses an electro-magnetic clutch to distribute the power to the wheels with the most grip. In "auto" mode and on dry roads more than 90 per cent of the power is fed to the rear wheels. The system offers both high and low gear ratios, the latter important for serious slow-speed, off-road work.