HUBLOCK Vacuum System Leak Test
NOTE:
This procedure requires the use of a calibrated vacuum gauge that is accurate to within a minimum of 0.1 in. Hg. It is recommended the Pressure Vacuum Module (105-R0099), or equivalent be used.
- Make sure hublocks are in the AUTO position. Lift and support the vehicle off the ground until the front tires can be spun freely.
- Start the engine and allow to idle. Turn the Mode Select Switch (MSS) to the 2WD position and wait 15 seconds. If switching from 4WD mode, wait an additional 45 seconds.
- Disconnect the vacuum line at the right front knuckle and install a vacuum gauge on the line. See Fig 1 . Disconnect the vacuum line at the left front knuckle and cap off the vacuum line. See Fig 2 .
- Turn the MSS to the 4WD position and observe the vacuum reading. The vacuum reading should remain at or above 10 in. Hg for 45 seconds.
- Turn the MSS to 2WD and observe the vacuum reading. The vacuum reading should remain between 5.8 and 7.3 in. Hg. for 15 seconds.
- Remove the vacuum gauge and connect the vacuum line at the right front knuckle. Turn the MSS to the 4WD position.
- Wait one minute then rotate the right front tire one revolution forward and one revolution backward, while observing the right front axle shaft and universal joint. The right front axle shaft and universal joint should turn.
- Turn the MSS to 2WD position. Wait one minute then rotate the right front tire one revolution forward and one revolution backward, while observing the right front axle shaft and universal joint. The right front axle shaft and universal joint should not turn.
- Install the vacuum pump and gauge line on the knuckle and pump to 20 in. Hg. See Fig 3 . If vacuum drop is greater than 0.5 in. Hg. in 30 seconds, go to next step. If vacuum drop is less than 0.5 in. Hg. in 30 seconds, check vacuum line connections and retest system.
- Remove the retainer ring and hublock assembly. See REMOVAL & INSTALLATION . Use a suitable vacuum cap to cap off wheel hub. See Fig 4 . Apply 20 in. Hg. to wheel hub. If vacuum drop is greater than 0.5 in. Hg. in 30 seconds, install a NEW hublock with a NEW "O" ring seal kit and retest. If vacuum drop is not greater than 0.5 in. Hg. in 30 seconds, install the hublock using a NEW "O" ring and retest system. If leak still persists, replace hublock. See REMOVAL & INSTALLATION .
- Repeat steps 1 - 10 for the left side hublock. If results are not as indicated, diagnose electrical components of the hublock system. See appropriate DIAGNOSIS article in TRANSFER CASE.
NOTE:
The engine is required to be at idle during the following steps to supply the vacuum required for the hublocks to engage and disengage.
NOTE:
Normal operation applies engagement vacuum for 45 seconds and then drops to 0 in. Hg.
NOTE:
Normal operation applies regulated disengagement vacuum for 15 seconds and then drops to 0 in. Hg.