Four Wheel Drive (4WD) Systems - Electronic Shift

Four Wheel Drive (4WD) Systems - Electronic Shift

Special Tool(s):

Principles of Operation

The electronic shift on the fly (ESOF) system is an electronic shift system that allows the operator to choose between 2 different four wheel drive (4WD) modes as well as two wheel drive (2WD). 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) and the transmission must be in NEUTRAL (or the clutch pedal pressed in manual transmission vehicles).

When the mode select switch (MSS) on the instrument panel is turned, the 4WD control module (PCM) activates the electromagnetic clutch and powers the transfer case shift motor. When the shift motor reaches the desired position, as determined by the contact plate position inputs to the 4WD control module (PCM), power to the shift motor will be removed. 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 select switch (MSS)
^ Wheel speeds (via high-speed controller area network [HS-CAN] communication from ABS module)
^ Contact plate position inputs A, B, C, D (grounded when closed, open circuit when open)
^ Transmission neutral

Feature Outputs

^ Transfer case synchronization clutch
^ Transfer case shift motor relays
^ Integrated wheel-end (IWE) vacuum solenoid
^ Instrument cluster (IC) indicators (via HS-CAN communication to IC)
^ 4WD mode (via HS-CAN communication to PCM)