Electronic Shift-On-The-Fly (ESOF) System

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 2-Wheel Drive (2WD). The operator can switch between 2H (4X2) and 4H (4X4 HIGH) mode at any forward speed. To engage or disengage 4L (4X4 LOW), the Transfer Case Control Module (TCCM) requires that the vehicle speed be less than 5 km/h (3 mph) and the transmission in NEUTRAL. This ESOF system includes a Constant Vacuum Hublock (CVH) system at the front wheel ends. The selector on the CVH, when turned fully counterclockwise to the AUTO position, engages/disengages the hub depending on the driver-selected 4WD mode of operation. The CVH also contains a manual override. When the selector is rotated fully clockwise to the LOCK position, the 4WD vacuum and electronic system used for coupling the front axle to the wheels is bypassed and the front wheels and front driveline remains coupled at all times.

The transfer case is equipped with a dual-cone synchronous clutch. This clutch is used to synchronize the front driveline to the rear driveline. All other internals operate in the same manner as the Manual Shift-On-Stop (MSOS) system. When the Mode Select Switch (MSS) on the instrument panel is turned, the TCCM powers the transfer case shift motor (part of the gearmotor encoder assembly), which activates a shift fork and engages the clutch. When the gearmotor encoder assembly reaches the desired position, as determined by the encoder position inputs to the TCCM, power to the gearmotor encoder assembly is removed. When the transfer case front and rear output shafts are synchronized, the lockup collar mechanically engages the mainshaft hub to the drive sprocket. At this point, the front axle CVH system is engaged. Instrument Panel Cluster (IPC) 4WD system indicator operation is controlled via the IPC which interprets outputs from the TCCM via the vehicle High Speed Controller Area Network (HS-CAN).