The Hummer H2 - 4WD SYSTEMS
The Hummer H2 has an electronically controlled transfer case to provide all-wheel drive (4-High), plus both 4-High lockup and 4-Low lockup. The transfer case is a novel Borg-Warner design. It's a planetary gearset in front for 4-Low gearing, and in the rear two partial planetary-type gearsets--suns and planets, but no ring gears, for open-or-lockup and 40/60 torque split. There are no clutches or bands. Shifting is done by an electric motor connected to forks that move gear-type shift collars. In front, the shift collar is splined on an intermediate shaft. With the shift collar in the forward position, the collar joins the input shaft to the intermediate shaft for a 1:1 torque transfer. Moving the collar back brings its gear teeth into mesh with the front carrier planet gears. The input shaft sun gear now transfers torque through the planets and their 2.64:1 reduction. The intermediate shaft transmits torque into the rear double planetaries. In the rear, the two planetaries are mated. The forward one has stepped gears and the smaller-diameter sections of the stepped gears mesh with the gears on the mating planetary, to produce the 40/60 torque split. The torque is transferred to both ends through primary output drive gears. When a shift collar at the rear is moved, the intermediate shaft is locked to the primary output drive gear in the main section of the transfer case. Because the primary output drive gear for the rear output shaft is chained to the one for the front output shaft, the front shaft is "locked" to the rear.

Ford and Warn Hubs have a revised vacuum-actuated automatic wheel-hub disconnect setup that leaves the entire front axle motionless in 2wd. The system has an electronically controlled multidisc clutch transfer case, and software that senses if the vehicle is off-road.

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