Four-Wheel Drive Systems: Notes

WARNING: This page is about a different variant/trim than selected.

The vehicle is equipped with an intelligent 4-wheel drive (4WD) system that is always active and requires no driver input. The system has no mode select switch. The system combines transparent all-surface operation with highly capable 4WD, and is capable of handling all road conditions, including street and highway driving as well as off-road and winter driving.

The 4WD system continuously monitors vehicle conditions and automatically adjusts the torque distribution between the front and rear wheels. During normal operation, most of the torque is sent to the front wheels. If wheel slip between the front and rear wheels is detected, or if the vehicle is under heavy acceleration (high throttle position), the 4WD system increases torque to the rear wheels to prevent or control wheel slip.

The 4WD system consists of a transfer case, rear driveshaft, coupling device, coupling device control module (4WD control module) and rear axle.

The 4WD control module varies the torque sent to the rear wheels by sending a duty cycle (percentage of time the coupling is turned ON) to the active torque coupling device located inside the rear axle. The 4WD control module also provides the brake system with its current clutch duty cycle and whether or not the brake system may take command of the clutch duty cycle.

NOTE: The active torque coupling is not repairable. If replacement is required, the active torque coupling and rear axle are replaced as an assembly. For additional information, refer to REAR DRIVE AXLE-DIFFERENTIAL .

The transfer case is a gearbox that attaches to the transaxle. On automatic transaxle vehicles, the right hand halfshaft passes through the transfer case and engages the differential side gear as in normal FWD applications. The transfer case directs power to the rear driveshaft through a helical gear spline coupled to the transaxle differential case, a helical gear drop (idler gear) and a hypoid/helical ring gear assembly and pinion set.

NOTE: Repair of the transfer case is limited to seals, gaskets and output flanges. If any of the geared components, bearings, case cover or internal shafts fail, a new transfer case must be installed.

The transfer case is sealed from the transaxle and has its own oil sump. The transfer case on an automatic transaxle vehicle uses 350 ml (12 oz.) of SAE 75W-140 gear lubricant. The transfer case on a manual transaxle vehicle uses 350 ml (12 oz.) of SAE 80W-90 gear lubricant.

The active, on-demand 4WD system uses data from other systems as inputs to the 4WD control module. The 4WD control module uses the inputs to determine the appropriate amount of current to send to the active torque coupling that delivers the desired torque to the rear wheels. Specific inputs to the 4WD control module are:

throttle position.
transaxle range from the powertrain control module (PCM).
brake system status from the anti-lock brake system (ABS).
wheel speed from all 4 wheels from the ABS. Some outputs of the 4WD control module are:
solid-state clutch (pulse-width modulated signal) to the active torque coupling.
4WD indicator received by the instrument cluster.
percent of torque transfer commanded signal to the PCM.
torque request available signal to the ABS.