A 4.0-liter, overhead-valve V6 engine powered all Explorers until 1996. With that engine a 5-speed manual gearbox was standard; 4-speed automatic transmission optional. In 1999 the 4-speed automatic was replaced by a 5-speed unit. A 210-horsepower V8 arrived for 1996. It was available only on 4-doors with the 4-speed automatic. In 1998 for added an overhead-cam 4.0-liter V6 mated only to a 5-speed automatic. Initially 4WD Explorers got Touch-Drive, a part-time system that engages or disengages 4WD by pushing a dashboard button. Budget-minded buyers could order a more elementary 4WD system, with a floor-mounted transfer-case lever and manually-selectable front hubs, as a credit option. Four-wheel-drive V8 models get a full-time all-wheel-drive system, and Ford also offered a full-time system called Control-Trac. The 4.0-liter ohc V6 engine became standard, replacing other available engines in 2001 Sport and Sport Trac models. A 4.6-liter V8 engine was available for 4-door models in 2002.