Electronic Shift System (NV271)
The electronic shift model transfer case features Electronic Shift-On-The-Fly (ESOF) system. This system uses electronic and vacuum-operated components to provide shifting between all transfer case ranges while vehicle is in motion. See Fig 1 . Driver selects transfer case mode through a 3-position rotary switch. Indicator light illuminates for each 4WD mode selected. Shifting into or out of 4X4 Low requires a vehicle speed less than 3 MPH, brake applied and transmission in Neutral or clutch pedal depressed. A digital Transmission Range (TR) sensor sends a signal to Generic Electronic Module (GEM) to indicate these conditions. An electronic shift motor is mounted on transfer case and drives a rotary cam to move mode fork and range fork between transfer case modes.
All shifting is accomplished through GEM module by input signals from multiple sensors and switches. GEM sends output signals to relays, solenoid and shift motor. ESOF system allows driver to control vacuum-operated hubs. When front hubs are manually turned to LOCK position, hubs are locked at all times, overriding the vacuum system. If front hubs are manually set to AUTO FREE, hubs can only be locked by selecting 4X4 HIGH or 4X4 LOW on mode select switch.