Transfer Case: IWE

WARNING: This page is about a different car, the 2018 Lincoln Navigator. However, it is still accessible from the selected car via links, so may be relevant.

Transfer case shift motor

The Borg-Warner 2-speed torque-on-demand transfer case is a 2-piece magnesium design. The transfer case transfers engine power from the transmission to the front and rear axles. Under normal driving conditions, the unit is in 2WD (2H), but when desired, the operator may shift into 4WD Auto (4A), 4WD High (4H) or 4WD Low (4L). When shifting into or out of LOW range, the TCCM requires that the vehicle speed is less than 5 Km/h (3mph) and the transmission is in NEUTRAL. The transfer case is equipped with an internal electromagnetic clutch that is activated electrically. In 4WD Auto (4A), the 4X4 control module varies the torque split between front and rear drivelines by controlling the transfer case clutch. Under most conditions, the 4X4 control module activates the transfer case clutch at a minimum duty cycle (percentage of time the clutch is turned on) which allows for a slight speed difference between the front and rear drivelines which normally occurs when negotiating a corner on dry pavement. When the rear wheels are overpowered for the available grip or handling event, the 4X4 control module detects this slip condition and the duty cycle to the transfer case clutch is increased until the speed difference between front and rear drivelines is reduced or the rotational speed is matched. In this manner, the 4X4 control module can redirect engine torque to the front wheels when the rear wheels lose traction, yet still allow operation in the 4WD Auto (4A) mode on dry pavement. The unit is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the rear output shaft.

One-Speed Torque-On-Demand

The 1-speed torque-on-demand transfer case consists of the following components:

Mode Select Switch (MSS)
Transfer Case Control Module (TCCM)
Integrated Wheel End (IWE) solenoid
IWE

The Borg-Warner 1-speed torque-on-demand transfer case is a 2-piece magnesium design. The transfer case transfers engine power from the transmission to the front and rear axles. Under normal driving conditions, the unit is in 2WD (2H), but when desired, the operator may shift into 4WD High (4H) and 4WD (4A) with Terrain Management System (TMS). The operator can switch between 2WD (2H), 4WD Auto (4A) and 4WD High (4H) at any speed. The transfer case is equipped with an internal electromagnetic clutch that is activated electrically. In 4WD Auto (4A), the 4X4 control module varies the torque split between front and rear drivelines by controlling the transfer case clutch. Under most conditions, the 4X4 control module activates the transfer case clutch at a minimum duty cycle (percentage of time the clutch is turned on) which allows for a slight speed difference between the front and rear drivelines which normally occurs when negotiating a corner on dry pavement. When the rear wheels are overpowered for the available grip or handling event, the 4X4 control module detects this slip condition and the duty cycle to the transfer case clutch is increased until the speed difference between front and rear drivelines is reduced or the rotational speed is matched. In this manner, the 4X4 control module can redirect engine torque to the front wheels when the rear wheels lose traction, yet still allow operation in the 4WD Auto (4A) mode on dry pavement. The unit is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the rear output shaft.

IWE

The IWE system consists of the following components:

Vacuum reservoir
Integrated Wheel End (IWE) solenoid
IWE (spring-loaded vacuum hubs)
Vacuum hoses
Check Valve

The IWE system uses vacuum hubs that engage or disengage the front wheel hubs from the front halfshafts.

The IWE solenoid receives engine vacuum from the vacuum reservoir.

When the 4WD system is in 2H mode, the TCCM supplies a ground path to the IWE solenoid to apply vacuum to the IWE (disengaging the front hubs from the front halfshafts). In a selected mode, the TCCM does not supply the ground path to the IWE solenoid, vacuum is not applied to the IWE and an internal spring keeps the front hubs engaged to the front halfshafts.