Electronic Shift-On-The-Fly (ESOF) System
Vehicles equipped with an ESOF system allow the operator to choose between 2WD and 2 different 4WD modes. The transfer case is shifted electronically by the TCCM based on the MSS position. Under normal driving conditions, the transfer case is in 2H (4X2), but when desired, the operator can shift into 4H (4X4 HIGH) or 4L (4X4 LOW). The operator can shift between 2H and 4H at any speed. To shift into 4L, the vehicle must be stopped or rolling less than 5 km/h (3 mph) and the transmission must be in NEUTRAL.
The message center of the IPC displays 4X4 SHIFT IN PROGRESS during a shift, then displays the system mode selected. If shift conditions are not met, the message center displays Information guiding the operator through the correct shifting procedures. If the message center displays SHIFT DELAYED PULL FORWARD, transfer case gear tooth blockage is present. To alleviate the condition move the vehicle forward approximately 1.5 m (5 ft) and if the condition occurs during a 4L shift, place the transmission in neutral to allow the transfer case to complete the shift and fully engage.
Continuous Vacuum Hublocks (CVH)
| Item | Description |
|---|---|
| 1 | Vacuum control solenoid. |
| 2 | Vacuum regulator valve. |
| 3 | Tube - Source vacuum to solenoid and reservoir. Includes one way check and regulator valves. |
| 4 | Vacuum reservoir |
| 5 | Vacuum tube nipple. |
| 6 | Front axle hublock - RH |
| 7 | Tube - Vacuum tube to steering arm / knuckle. |
| 8 | Vacuum tube assembly. |
| 9 | Front axle hublock - LH |
| 10 | Steering arm / knuckle. |
| 11 | "O" Ring. |
| 12 | Wheel hub |
| 13 | "O" Ring Kit |
| 14 | Front axle hublock |
The continuous vacuum hublocks (CVH) system uses a vacuum solenoid and vacuum actuated hubs to engage or disengage the front wheel hubs from the front half shafts.
When the 4WD system is in 2WD (2H) mode, the TCCM does not supply the ground path to the CVH solenoid. Vacuum is not applied to the CVH. An internal spring keeps the CVH disengaged.
When operating in any 4WD mode, the TCCM supplies a ground path to the CVH solenoid to apply vacuum to the CVH thus engaging the front hubs to the front axle shafts. To maintain vacuum during all modes of engine operation, a one way vacuum check valve and a vacuum reservoir are positioned between the vacuum source and the CVH solenoid. The CVH require 6 inHg of vacuum to engage. A vacuum regulator valve positioned downstream from the CVH solenoid limits CVH vacuum to approximately 10 inHg. Some engines are equipped with a mechanical vacuum pump that supplies vacuum to the CVH vacuum reservoir.
The CVH may also be mechanically engaged by rotating the CVH dial to the LOCK position. In the LOCK position, the front hubs will be engaged to the front axle shafts regardless of vacuum supply.