The transfer case (7A195) is equipped with a magnetic clutch, similar to an air conditioning compressor clutch, which is located inside the transfer case adjacent to the lockup sleeve. The clutch is used to spin up the front drive system from zero to vehicle speed in milliseconds. This spin-up allows the shift between 2H and 4H to be made at vehicle speeds listed in the vehicle owner's guide. The spin-up engages the front lock hubs. When the transfer case rear and front output shaft reach synchronous speed, the spring-loaded shift collar mechanically engages the mainshaft lockup hub to the chain-drive sprocket and the magnetic clutch is then deactivated. Shifts between 4H and 4L can only occur with the transmission safety switches closed. The vehicle's speed must also be within specified limits as determined by the Generic Electronic Module (GEM).
The electronic shift control system consists of a rotary switch control system, a GEM, a transfer case shift motor (7G360) with an integral shift position sensor, a clutch pedal position switch or digital transmission range (DTR) sensor, and a brake signal input switch.
There is a control switch located on the instrument panel for fingertip shift control.
Switch Control System
When the switch on the instrument panel is turned, there is a one second delay, then the electronic control module verifies the transfer case positions (2H, 4H or 4L). Next, the GEM looks at the shift position sensor and the digital transmission range (DTR) sensor or clutch pedal position switch (depending on transmission type) and brake pedal switch. If all conditions are correct to allow the desired shift, the electronic control module will tell the transfer case shift motor to execute the shift. After the shift has been made and the transfer case shift motor is off, the control module again looks at the shift position sensor to make sure the proper shift has been accomplished. Finally, the dash indicator light on the control panel will be illuminated by a signal from the GEM indicating the desired shift has been completed.
The generic electronic module controls the operation of the transfer case in response to inputs to the rotary control by the vehicle operator, the shift position sensor, the transmission range sensor and the brake pedal switch.
Vehicle Speed Sensor (VSS)
The vehicle speed sensor (VSS) (9E731) generates an AC signal which is sent to the instrument cluster (10849). The signal is used as input to the powertrain control module (PCM) and the transmission control module (TCM).
Shift Position Sensor
The shift position sensor, an integral part of the electric shift motor, tells the GEM module the shift position of the transfer case.
Electric Shift Motor
The electric shift motor, mounted externally at the rear of the transfer case, drives a rotary helical cam which moves the 2W-4W shift fork and 4H-4L reduction shift fork to the selected vehicle drive position.
does it jump out of gear or just doesn't go into gear in the first place ?
- 4-Wheel Drive Transfer Case Jumps Out of Gear
- Incomplete shift linkage travel.
- ADJUST linkage to provide complete gear engagement. ADJUST shift gearshift lever boot.
- Front and rear driveshaft slip yokes dry or loose.
- LUBRICATE and REPAIR slip yokes as required. TIGHTEN flange yoke attaching nut to specifications.
- DISASSEMBLE transfer case. INSPECT sliding clutch hub and gear clutch teeth for damage. REPLACE as required.