Electronic Shift Control System: 1354
Electronic shift control system is also known as Touch-Drive. Electromagnetic clutch is used to spin-up front drive output from zero to vehicle speed in less than a second. This spin-up allows the 2WD to 4WD shift to be made at any speed.
When transfer case rear and front output shafts reach the same rotating speed, spring-loaded shift collar mechanically engages mainshaft hub to chain drive sprocket. Magnetic clutch is then deactivated. Shifts between 4WD high and 4WD low only occur with clutch pedal depressed (M/T) or transmission range sensor in park or neutral and vehicle speed 3 MPH or less.
The Generic Electronic Module (GEM) acts as the microcomputer for transfer case shifting operations. GEM makes shifting decisions based on inputs from 4WD switch, transmission range, transfer case range, vehicle and driveshaft speed, clutch and brake inputs. GEM also has self-diagnostic capabilities. Electronic shift control module contains relays that power shift motor. Actual shifting is carried out by electric motor mounted on the transfer case. See Fig 1 . Electric motor turns linkage which moves shift fork causing drive sprocket to lock on front output shaft.