Axle Shift Motor Functional Test
- Raise vehicle. Disconnect vacuum harness from axle shift motor and connect a vacuum pump to vacuum shift motor port. See Fig 1
.
- Apply 15 in. Hg. (51 kPa) of vacuum to front port and rotate right front wheel to fully disengage outer and intermediate axle shafts (e.g., into two wheel drive operation).
- The shift motor should maintain vacuum applied to front port for a minimum of 30 seconds. If motor does not maintain vacuum, replace it. If motor does maintain vacuum, proceed to next step.
- Disconnect vacuum pump from vacuum shift motor front port. See Fig 1
. Connect vacuum pump to vacuum shift motor rear port, cap port for indicator lamp sw., and apply 15 in. Hg (51 kPa) of vacuum to rear port.
- The shift motor should maintain the vacuum applied to rear port for a minimum of 30 seconds. If shift motor does not maintain vacuum, replace it. If motor does maintain vacuum, proceed to next step.
- Remove cap from port for indicator lamp sw. and determine if vacuum was present at this port. If vacuum was present, the shift motor functions normally. If vacuum was not present, proceed to next step.
- Apply 15 in. Hg. (51 kPa) of vacuum to shift motor rear port. Rotate right front wheel as necessary and ensure that outer and intermediate axle shafts are completely engaged. The axles must be completely engaged (i.e. into four-wheel drive operation) to open port for indicator lamp switch.
- Determine if vacuum is present at port for indicator lamp switch again. If vacuum was present at port, shift motor functions normally. If vacuum was not present at port, replace shift motor.
Courtesy of DAIMLERCHRYSLER CORP.