Four Wheel Drive (4WD) Systems - Mechanical Shift

Principles of Operation

Special Tool(s):

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 (2WD) and NEUTRAL. This system does not utilize a 4X4 control module. The operator can switch between two wheel drive high (2H), NEUTRAL (N), four wheel drive high (4H) and four wheel drive low (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 (IC) 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 2H, but when desired, the operator may shift into 4H or 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
^ IC indicators (signals are hardwired to the IC via the MIS)
^ Manual hublocks

Inspection and Verification
1. Visually inspect for obvious signs of mechanical and electrical system concerns.

Visual Inspection Chart

Visual Inspection Chart:

2. Carry out the Mechanical Shift-On-Stop (MSOS) Functional Test. GO to Pinpoint Test F. Test F: Mechanical Shift-On-Stop (MSOS) Functional Test
3. If the concern is still present after the Mechanical Shift-On-Stop (MSOS) Functional Test, GO to Symptom Chart - Mechanical Shift. Symptom Chart - Mechanical Shift