Explorer 4WD V6-245 4.0L (1991)
Tires: All Technical Service Bulletins
Transfer Case - Unable to Disengage 4WD Into 2WD
Article No.
91-20-17
10/02/91
TRANSFER CASE - 4X4 - UNABLE TO DISENGAGE
LIGHT TRUCK:
1990-91 RANGER 1991 EXPLORER
ISSUE:
The vehicle may remain in 4 Wheel Drive after the transfer case has been shifted back into 2WD. This may occur because of uneven tire
wear, the front axle hubs not disengaging, or the return spring force not being sufficient to move the lock-up fork back to the 2WD position.
ACTION:
Inspect the vehicle tires for wear and, if necessary, replace the return spring, sleeve spring and lock-up fork in the transfer case.
INITIAL CHECKS
1.
Rotate the tires and check for evidence of an uneven wear band or spots.
2.
Set the tire pressure as specified on the safety compliance certification label.
3.
Confirm that the tires are matched in design, size and manufacture.
4.
Confirm by hand rotation that the front axle automatic and manual locking hubs are disengaging correctly.
NOTE: IF THE VEHICLE WAS PREVIOUSLY REPAIRED PER TSB 91-15-10, THE TRANSFER CASE WAS UPDATED WITH THE PARTS
INCLUDED IN THIS TSB. IF THE UPDATED TRANSFER CASE STILL WILL NOT DISENGAGE AFTER FOLLOWING THE INITIAL
CHECKS, THEN THE CAUSE COULD BE THAT THE DRIVER IS NOT ALLOWING SUFFICIENT TIME FOR THE 4WD SYSTEM TO
DISENGAGE.
VERIFICATION
Drive the vehicle. If the transfer case still will not disengage after performing the initial checks, proceed as follows:
1.
Shift the vehicle with lever operated or electric shift transfer case to 4WD high.
2.
Hand rotate the front axle manual locking hubs to the lock position, if so equipped.
3.
Drive the vehicle slowly in a tight turn on dry hard pavement until you feel the front wheel power hop/skip which indicates that the 4WD system is
engaged.
4.
Drive the vehicle on a frame hoist...
a.
Shift the automatic or manual transmission to neutral.
b.
Shift the transfer case to 2WD.
c.
Turn the ignition key to the OFF position.
5.
Raise the vehicle on the frame hoist, making sure all tires are free to rotate.
6.
Using gloves, hand rotate the rear driveshaft while viewing the front driveshaft for rotation.
^
If the front driveshaft does not rotate, this indicates that the transfer case has disengaged and is functioning correctly.
^
If the front driveshaft rotates while turning the rear driveshaft, this indicates that the transfer case has not disengaged and must be repaired.
7.
Before starting the repair, repeat the above procedure a second time to confirm that the transfer case will not disengage.
ELECTRIC SHIFT TRANSFER CASE
If the above procedure is not conclusive, for an electric shift transfer case system, proceed as follows:
