Principles of Operation

Principles of Operation

Mechanical Operation
In the 2WD mode, torque from the engine is transferred through the transmission to the transfer case, which in turn drives the output shaft that drives the rear axle.

The 2WD to 4WD HIGH shift is accomplished when the 2WD to 4WD HIGH shift fork moves the mode sleeve to engage the drive sprocket to the rear output shaft. The drive sprocket turns the chain which turns the front output shaft driven sprocket on the front output shaft and the front driveshaft.

The 4WD HIGH to 4WD LOW shift is accomplished when the 4WD HIGH to 4WD LOW shift fork moves the range sleeve to engage the planet carrier to the main shaft. Torque for the input shaft is then transmitted through the sun gear, which then turns the planets. The planets, which are now engaged to the output shaft, provide a gear reduction.

The electronic- shift four-wheel drive system consists of the following components:
^ transfer case
^ four wheel drive control module.
^ Mode Select Switch (MSS)
^ gearmotor encoder assembly

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

2-Wheel Drive
When 2WD is selected, the range sleeve at the center of the front planet slides forward, putting the transfer case 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 mode sleeve is disengaged so none of the 4-wheel drive components turn.

4-Wheel Drive - 4WD HIGH
In 4WD HIGH, the range sleeve remains in the same position as it was in 2WD. The action of the shift lever causes the mode sleeve to move rearward, locking the drive sprocket and chain to the rear output shaft. This causes both the front and rear wheels to be driven in the high range.

4-Wheel Drive -4WD LOW
4WD LOW allows for maximum pulling capacity. Shifting into 4WD LOW causes the range sleeve to move rearward and engage the planetary gear to achieve gear reduction. The result is that the output shaft now turns more slowly than the input shaft. This action increases the pulling capacity available to the wheels.