Four Wheel Drive (4WD) Systems - Mechanical Shift

Four Wheel Drive (4WD) Systems - Mechanical Shift

Special Tool(s):

Principles of Operation

The mechanical shift on the fly (MSOF) system is a manual shift four wheel drive (4WD) system that allows the operator to chose between 2 different 4x4 modes as well as two wheel drive and NEUTRAL. The operator can switch between 2H and 4H mode at speeds up to 88 km/h (55 mph). To engage or disengage 4L range, the vehicle speed must be less than 5 km/h (3 mph), the brake pedal pressed and the transmission must be in NEUTRAL (or the clutch pedal pressed in manual transmission vehicles).

The transfer case is equipped with an electromagnetic clutch which is located inside the case. This clutch is used to synchronize the front driveline. When the manual shift lever is moved, this activates the mode indicator switch, triggering the 4WD control module (PCM) to energize the electromagnetic clutch. When the transfer case front and rear output shafts are synchronized, the spring loaded lockup collar mechanically engages the mainshaft hub to the drive sprocket. Finally, the front axle integrated wheel ends (IWEs) are engaged and the electromagnetic clutch is deactivated.

Feature Inputs

^ Mode indicator switch
^ Wheel speeds (via high-speed controller area network [HS-CAN] communication from ABS module)

Feature Outputs

^ Transfer case synchronization clutch
^ IWE vacuum solenoid
^ 4WD mode (via HS-CAN input to PCM)
^ Instrument Cluster (IC) indicators (via HS-CAN communication to the IC)