Section 07-07A: Transfer Case, Electronic Shift | 1996 F-150 4x4 Vehicles with Automatic Transmissions and All Bronco Vehicles Workshop Manual |
The Borg-Warner 13-56 Electronic Shift Transfer Case (7A195) transfers power from the transmission (7003) to the rear axle assembly (4006) and to the front axle when electronically actuated. The 13-56 provides for low range driving. The system has no selectable neutral.
Mechanical Operation
In the 4x2 mode, torque from the transmission is transferred to the front input shaft (7017), which in turn drives the rear output shaft that drives the rear axle.
The 2W-4W shift is accomplished when the 2W-4W shift fork moves the lockup collar to engage the front drive sprocket on the output shaft splines. The front drive sprocket turns the chain, which turns the front output shaft driven sprocket on the splined front output shaft and the front driveshaft.
The high-low shift is accomplished when the high-low shift fork moves the shift collar to engage the front planet (7A398) to the output shaft. Torque from the input shaft is then transferred through the sun gear, which then turns the front planet. The front planet, which is now engaged to the output shaft, provides the gear reduction.
The unit is lubricated by a positive displacement oil pump that channels oil through the bores in the output shaft.
Electronic Shift Operation
The transfer case is equipped with a magnetic clutch, similar to an air conditioning compressor clutch, which is located inside the transfer case adjacent to the lockup collar. The clutch is used to spin up the front drive system from zero to vehicle speed in milliseconds. This spin-up allows the shift between 2-high and 4-high to be made at any vehicle speed. The spin up engages the front lock hubs. When the transfer case rear and front output shafts reach synchronous speed, the spring-loaded lockup collar mechanically engages the mainshaft hub to the chain drive sprocket and the magnetic clutch is then deactivated. Shifts between 4-high and 4-low can only occur with the transmission safety switches closed and the vehicle at a full stop.
When a control switch on the instrument panel is depressed, the electronic control module will analyze certain input information and, if all the design conditions are met, the electronic control module will command the electric shift motor to execute the desired function. The inputs required by the electronic control module are from the:
After the shift takes place and the motor is turned off, the electronic control module will again look at the inputs from the shift position sensor to determine if the transfer case is in the position that the operator selected. Finally, the electronic control module will illuminate the shift indication lights located on the electronic switch control and the instrument panel to indicate that the desired function has been completed.
When the operator selects the drive combination through the push-button control, an electric motor turns a helical cam, which is linked to the high-low and 2W-4W shift forks through gearshift lever socket bushings. As the electric motor turns the helical cam, the high-low fork gearshift lever socket bushing rides in a slotted lobe in the cam to make the low-high or high-low range change. The 2W-4W fork gearshift lever socket bushing rides on lobes at the end of the cam to make the 2W-4W or 4W-2W shift.