Electronic Shift Control System Components
Transfer Case
Motor, Electric Shift
The transfer case shift motor (7G360) a mounted externally at rear of the transfer case (7A195). It drives the shift cam assembly which moves the 4WD high/4WD low shift reduction fork for desired vehicle operation An integral position senor provides information to the generic electronic module (GEM) for motor position.
Switch, Control System
Switch, Rotary Control
The rotary control switch is located on the instrument panel. The switch consists of a knob with a night-time illuminated pointer. The switch is used to select the Auto, High, and Low positions on the instrument panel. The indicator light will illuminate when the 4WD Auto or 4WD Low positions are engaged.
Sensor, Digital Transmission Range (DTR)
The DTR sensor is located on the outside of the transmission at the manual lever. The DTR sensor completes the start circuit in PARK and NEUTRAL, the back-up lamp circuit in REVERSE and the neutral sense circuit (4WD) in NEUTRAL. The DTR sensor also sends a digital output signal to the powertrain control module (PCM) (12A650) indicating the position of the manual lever (P, R, N, D, 2, 1).
Switch, Clutch Pedal Position (CPP)
The clutch pedal position (CPP) switch is located on the clutch pedal bracket. On vehicles equipped with a manual transmission (7003) and an electronic shift transfer case, the clutch pedal must be fully depressed and vehicle stopped in order to make a range shift from HIGH to LOW, or from LOW to HIGH.
Generic Electrical Module (GEM)
The GEM controls the operation of the transfer case in response to inputs from the Brake ON/OFF (BOO) switch, the DTR sensor/CPP switch and electric shift transfer case through the actuation of the range switch.
Electronic Shift Control System Components
The Borg-Warner 44-05 transfer case is used in the Explorer (4WD) vehicle. The transfer case transfers power from the transmission to the rear axle, and also to the front axle when electronically activated.
MECHANICAL OPERATION
In the 4X2 mode, torque from the transmission is transferred to the input shaft which, in turn, drives the rear output shaft that drives the rear axle assembly. The 2WD through 4WD auto shift is accomplished through an electromechanical ball ramp clutch assembly.
The electromechanical ball ramp clutch assembly drives the drive sprocket after the Generic Electronic Module (GEM) activates the clutch coil. The drive sprocket turns the chain which rotates the front output shaft and front driveshaft.
The high-low shift is accomplished when the reduction shift fork moves the reduction collar to lock the planetary gear set to the output shaft. Torque from the input shaft is then transmitted through the sun gear, which then turns the front planetary gear set front planet. The front planetary gear set front planet which is now engaged provides transfer case speed reduction.
TRANSFER CASE FUNCTIONS
There are three modes on the transfer case, Auto, 4WD Low, and 4WD High. Neutral is only available as a dealer installed option.
C-TRAC FUNCTION
The C-Trac transfer case transmits torque to the front wheels through an electromechanical clutch assembly. In the Auto mode, while at rest and under cruising conditions, the Generic Electronic Module (GEM) activates the transfer case clutch at a minimum level. This allows for the slight difference between the front and rear driveshafts which occurs normally when negotiating a comer on dry pavement. Under any of the following conditions, the GEM will increase the torque sent through the clutch to the front wheels in order to prevent or control slip.
- Slip is detected (by monitoring the Hall Effect Sensors in the transfer case)
- Heavy acceleration (by using the throttle position signal from the EEC)
- Very light or zero throttle at speeds above 64 km/h (40 mph) (using the throttle position signal from the EEC)
RANGE FUNCTION
In the 4WD Low Range, the transfer case electromechanical clutch locks the front and rear driveshafts for maximum 4WD traction. The transfer case motor also rotates the shift cam to move the reduction fork to the 4WD low range position. This low range shift is accomplished through a planetary gear set which changes the torque to the driveshaft from 1:1 to 2.48:1 ratio.
In the 4WD High Range, the GEM locks the front and the rear driveshafts for maximum 4WD traction. This position is not meant for use on dry or merely wet pavement. It is intended for off-road or severe winter weather use only.