Mechanical Operation

In the 4x2 mode, torque from the transmission (7003) is transferred to the front input shaft, which in turn drives the output and fifth gear drive shaft (7061) that drives the rear axle.

The 2W-4W shift is accomplished when the 2W-4W shift fork moves the lockup collar to engage the drive sprocket on the rear output shaft splines. The drive sprocket turns the chain which turns the front output shaft driven sprocket on the front output and fifth gear drive shaft and the front driveshaft.

The high-low shift is accomplished when the high-low shift fork moves the shift collar hub to engage the front planet (7A398) to the output and fifth gear drive shaft. Torque for the input shaft (7017) is then transmitted through the sun gear, which then turns the front planet. The front planet, which is now engaged to the output and fifth gear drive shaft, provides a reduction.

Neutral

With the shift selector in neutral, no power is transmitted to either front or rear. All the planetary gears turn freely with the input shaft, and the chain sprocket floats freely on the output and fifth gear drive shaft.

Power Flow in Neutral

The following illustration shows a cross-section of the front planet. At the center, attached to the input shaft, is the sun gear. This gear meshes with four gears that surround it like planets (which is why this component is called a planetary gear). In turn, the four gears mesh with an outer gear called the ring gear (7A153).

The sun gear rotates at the speed of the transmission output. The ring gear is stationary. The front planet assembly rotates with the planetary gears as they "walk" around the inside of the ring gear to provide the gear reduction. If the output shaft is locked to the sun gear, as in high range, the output rotates at transmission output speed. If the output is locked to the front planet assembly, as in low range, the output rotates at the reduction rate.

2-Wheel Drive — High Range

When the driver selects 2H, the shift collar hub at the center of the front planet slides forward, putting the transfer case (7A195) into the high speed range (direct drive). The input shaft and the rear output shaft are locked together. This results in direct drive, straight through to the rear driveshaft. In addition, the 4-wheel drive lockup collar is disengaged so none of the 4WD components turn.

Power Flow in 2H

4-Wheel Drive — High Range

In 4-wheel drive — high range (4H), the front planet stays where it was in the 2H shift. The action of the shift lever causes the 4-wheel drive lockup hub to move rearward, locking the chain sprocket to the rear output shaft. Now, both the rear and the front wheels are being driven in the high range.

Power Flow in 4H

4-Wheel Drive — Low Range

To get maximum pulling capacity, the driver selects 4L. When this happens, the shift collar hub moves rearward, and the front planet is locked to the output and fifth gear drive shaft. With the ring gear unable to turn, the planetary gears "walk" around the inside. The result is that the front planet now turns more slowly than the input shaft. Because the front planet is now locked to the output and fifth gear drive shaft, the output shaft now rotates at a slower speed than the input shaft. This action increases the pulling capacity available to the wheels.

Power Flow in 4L