Four Wheel Drive (4WD) Systems - Mechanical Shift

Four Wheel Drive (4WD) Systems - Mechanical Shift

Principles of Operation

Mechanical Shift-On-Stop (MSOS) System

The mechanical shift-on-stop (MSOS) system allows the operator to manually choose between 2 different 4x4 modes as well as two wheel drive (2H) and NEUTRAL. This system does not utilize a 4WD control module. The operator can switch between 2H, N, 4H and 4L at speeds below 5 km/h (3 mph). To engage or disengage 4L, the transmission should be in NEUTRAL to alleviate residual drag torque created by the engine. This system contains manual hublocks. Prior to shifting to 4H and 4L, the front axle must be coupled to the hubs by rotating the hublocks fully clockwise to the "Lock" position.

The transfer case contains a non-synchronous clutch and Ford recommends that range shifts be carried-out at or below 5 km/h (3 mph) to prevent excessive transfer case engagement noise. When the manual shift lever is moved to 4H, the mode sleeve is moved rearward, locking the drive sprocket and chain to the rear output shaft. Moving the lever further to 4L causes the range sleeve to move rearward and engage the planetary gear set. This causes the output shaft to turn more slowly than the input shaft, resulting in increased pulling capacity at the wheels. The shift lever also operates the mode indicator switch, which triggers the instrument cluster to energize the "4x4" and/or "Low Range" indicator.

Mechanical Shift Transfer Case

The mechanical shift transfer case is a 3-piece aluminum design. The unit transfers engine power from the transmission to the front and rear axles. Under normal driving conditions the unit is in two wheel drive high (2H), but when desired, the operator may shift into four wheel drive high (4H) or four wheel drive low (4L). The transfer case is shifted manually. The unit is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the mainshaft.

Feature inputs:
^ Mode indicator switch (MIS)

Feature outputs:

^ Transfer case non-synchronous clutch
^ Instrument cluster indicators (signals are hardwired to the instrument cluster via the MIS)
^ Manual hublocks