Ford F150 Pickup. Instruction - part 1933

Fig. 2: Transfer Case Power Flow In 4H 
Courtesy of FORD MOTOR CO. 

In 4-wheel drive - high range (4H), the (A) 4-wheel drive lockup hub moves rearward and locks the (B) chain 
sprocket and (C) chain to the (D) rear output shaft. Both the (D) rear output shaft and (E) front output shaft are 
being driven in high range. The (F) reduction hub is in the forward position. 

Power Flow In 4L 

 

2003 Ford Pickup F150 

2003 TRANSMISSIONS Transfer Case - General Information - F150 Pickup

  

Fig. 3: Transfer Case Power Flow In 4L 
Courtesy of FORD MOTOR CO. 

In 4-wheel drive - low range (4L), the (A) reduction hub moves rearward and the (B) low range gearset is 
engaged to the (C) rear output shaft. The ring gear is locked and results in the (B) front planet gear turning 
slower than the (D) input shaft. This in turn makes the (C) rear output shaft and (E) front output shaft turn at a 
slower speed than the (D) input shaft. This action increases the pulling power available to the wheels. 

TRANSFER CASE - MECHANICAL SHIFT ON THE FLY (MSOF) OPERATION 

The Mechanical Shift On the Fly (MSOF) system is a instruction shift 4WD system that allows the operator to 
chose between two different 4x4 modes as well as 2-wheel drive. The operator can switch between 2WD and 
4H mode at speeds up to 88 km/h (55 MPH). To engage or disengage 4L range, the vehicle speed must be less 
than 5 km/h (3 MPH), the brake pedal depressed, and the transmission must be in NEUTRAL. 

Shifts between 2H and 4H can be made at a stop or any forward speed up to 88 km/h (55 MPH). At 
temperatures below 0°C (32°F) shifts should not be performed above 72 km/h (45 MPH). 

The transfer case is equipped with an electromagnetic clutch which is located inside the case. This clutch is 
used to spin up the front driveline when shifting from 2WD to 4x4 mode at speed. When the instruction shift lever 
is moved, this activates the 4WD indicator switch, 4WD electric clutch relay, and the electromagnetic clutch. 
When the transfer case front and rear output shafts are synchronized, the spring loaded lockup collar 
mechanically engages the mainshaft hub to the drive sprocket. Finally, the front axle collar is engaged and the 

 

2003 Ford Pickup F150 

2003 TRANSMISSIONS Transfer Case - General Information - F150 Pickup

  

electromagnetic clutch is deactivated. 

TRANSFER CASE - ELECTRONIC SHIFT ON THE FLY (ESOF) OPERATION 

The Electronic Shift On The Fly (ESOF) system is an electronic shift 4x4 system that allows the operator to 
choose between two different 4x4 modes as well as 2-wheel drive. The operator can switch between 2WD and 
4H mode at speeds up to 88 km/h (55 MPH). To engage or disengage 4L range, the vehicle speed must be less 
than 5 km/h (3 MPH), the brake pedal depressed, and the transmission must be in NEUTRAL. 

The transfer case is equipped with an electromagnetic clutch which is located inside the case. This clutch is 
used to spin up the front driveline when shifting from 2WD to 4H mode at speed. When the control switch on 
the instrument panel is turned, the Generic Electronic Module (GEM) recognizes that a shift has been requested 
and activates the electromagnetic clutch and the relays which power the transfer case shift motor. When the 
shift motor reaches the desired position, as determined by the contact plate position inputs to the GEM, power 
to the shift relays and motors will be removed. When the transfer case front and rear output shafts are 
synchronized, the spring loaded lockup collar mechanically engages the mainshaft hub to the drive sprocket. 
Finally, the front axle collar is engaged and the electromagnetic clutch is deactivated. 

Shifts between 2WD and 4H can be made at any speed up to 88 km/h (55 MPH). Listed below are the inputs 
and outputs needed by the GEM to execute a change between any of these modes. 

Feature Inputs:  

z

4WD mode switch (various resistances; go to Table 1 - 4WD Mode Switch Input Resistances ).  

z

Contact plate position inputs A, B, C, D (grounded when closed, open circuit when open; go to Table 4 - 
Contact Plate Sensor Position Codes ).  

Feature Outputs:  

z

4x4 shift motor relay outputs (go to Table 2 - Transfer Case Shift Relays Outputs ).  

z

Transfer case clutch relay (grounded when relay is activated, open circuit when relay is deactivated).  

z

4x2/4x4 vacuum solenoid (grounded when activated, open circuit when deactivated).  

z

Cluster indicators (ground when activated, open circuit when deactivated).  

When shifting into or out of 4L, the GEM requires that the vehicle speed be less than 5 km/h (3 MPH), the 
brake is applied, and the transmission is in NEUTRAL. 

Feature Inputs:  

z

4WD Mode Switch (various resistances; go to Table 1 - 4WD Mode Switch Input Resistances ).  

z

Contact Plate Position Inputs A, B, C, D (grounded when closed, open circuit when open; go to Table 4 - 
Contact Plate Sensor Position Codes ).  

z

Output Speed Shaft (OSS) Sensor (Sinusoid Signal: 0.7V-20V, 2.2 Hz/MPH).  

z

Brake Input (battery voltage when brake is depressed, open circuit when not activated).  

z

Transmission Range Sensor (grounded when transmission is in NEUTRAL, open circuit otherwise). 

 

2003 Ford Pickup F150 

2003 TRANSMISSIONS Transfer Case - General Information - F150 Pickup

  

z

Start/Clutch Depressed Input (go to Table 3 - Neutral Safety Switch Input Conditions ). Feature 
Outputs:  

z

4x4 Shift Motor Relay Outputs (go to Table 2 - Transfer Case Shift Relays Outputs ).  

z

4x2/4x4 Vacuum Solenoid (grounded when activated, open circuit when deactivated).  

z

Cluster Indicators (grounded when activated, open circuit when deactivated).  

TRANSFER CASE - ELECTRONIC SHIFT ON THE FLY (ESOF) FEATURES 

A rotary switch allows the vehicle operator to choose between 2WD, 4H, and 4L modes of 4x4 operation. 

DIAGNOSIS & TESTING 

TRANSFER CASE - ESOF 

Refer to TRANSMISSION for schematic and connector information. 

The Generic Electronic Module (GEM) controls the operation of the 4x4 system. 

The Output Shaft Speed (OSS), mounted in the rear of the transfer case, informs the GEM of the vehicle speed. 

The shift motor sense plate, an integral part of the electronic shift motor, informs the GEM to the positions of 
the transfer case (go to Table 4 - Contact Plate Sensor Position Codes ). 

The transmission range sensor is located on the LH side of the transmission; this sensor informs the GEM when 
the transmission is in the NEUTRAL position. 

The electronic shift motor, mounted externally at the rear of the transfer case, drives a rotary cam which moves 
the mode fork and range fork within the transfer case to select between the 2WD, 4H, and 4L positions. 

The 4x4/4x2 vacuum solenoids are attached to the upper RH side of the engine compartment, and alternately 
route vacuum to the vacuum motor which engages/disengages the center axle disconnect collar in the front axle 
assembly. 

The 4x4 shift motor relay is a module containing two relays. Under the control of the GEM, the 4x4 shift motor 
relay shifts the transfer case shift motor between the 2WD, 4H, and 4L modes. 

The transfer case clutch relay is an electromechanical relay used to activate the transfer case clutch within the 
transfer case. 

Special Tool(s) 

 

2003 Ford Pickup F150 

2003 TRANSMISSIONS Transfer Case - General Information - F150 Pickup