Electronic Shift Control System: 44-05
The electronic shift control system on Explorer is also known as Control-Trac. When in auto 4WD, system uses front and rear driveshaft speed sensors to compare front and rear driveshaft speeds. When driveshaft speeds differ by a predetermined amount Generic Electronic Module (GEM) activates electromagnetic clutch to lock transfer case and equalize driveshaft speed.
Shifting between ranges is accomplished by GEM interpreting signals from 4WD selector, vehicle speed sensor, front and rear driveshaft hall sensors, and transfer case contact plates. Based on these signals, power is directed through relays to turn 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. GEM also has self-diagnostic capabilities.