Disconnect the vacuum harness from the transfer case shift motor.
Connect Vacuum Pump J-23738 to the shift motor front port. Refer to the Vacuum Diagrams.
Apply 51 kPa (15 in) of vacuum to the shift motor and rotate the rear propeller shaft to fully engage the transfer case in the four-wheel drive mode. The shift motor should maintain vacuum applied to the front port for a minimum of 30 seconds. If the shift motor does not maintain vacuum, replace the motor. If the motor does maintain vacuum, proceed to the next step.
Disconnect the vacuum pump from the shift motor front port. Connect the pump to the shift motor rear port, plug the front axle connecting port and apply 51 kPa (15 in) of vacuum to the motor.
Shift an automatic transmission into Park. Shift a manual transmission into first gear.
The shift motor should maintain vacuum applied to the rear port for a minimum of 30 seconds. If the shift motor does not maintain vacuum, replace the motor. If the motor does maintain vacuum, proceed to the next step.
Remove the cap from the shift motor axle connecting port and check for vacuum at the port. If there is no vacuum at the port, rotate the rear propeller shaft, as necessary, to ensure complete transfer case engagement.
NOTE: The transfer case must be completely engaged before the shift motor stem will extend fully and open the axle interconnecting port.
If vacuum is now present at the shift motor axle connecting port after fully engaging the transfer case, refer to the service diagnosis charts.
If vacuum is still not present at the shift motor axle connecting port, slide the boot away from the shift motor stem and measure the distance the stem has extended. The stem should extend a distance of 15.88 mm (5/8 in) as measured from the edge of the shift motor housing to the E-ring on the stem.
If the shift motor stem does not extend to the specified distance, refer to the service diagnosis charts.
If the shift motor stem does extend to the specified distance but vacuum is still not present at the axle connecting port, replace the motor.
Click for a cut-away view of the transfer case
shift motor
V 980923