Bearing Or Metallic Grinding Sound While Operating In Auto 4HI Or 4LO Modes - keywords grind growl noise

This PI was superseded to add models and note. Please discard PIP4146A.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some customers may comment about a noise in the transfer case in either AUTO or 4WD. This may sound like a noisy bearing or a metallic grinding sound. It may also be accompanied by a C0327 DTC. The transfer case noise may be caused by an apply plate bearing failure. As pressure gets applied to the clutch pack the apply plate bearing gets loaded. Continuous operation in either AUTO or 4WD shortens the life of the bearing.

Note: Although there will be some characteristic noise while operating in 4wd, a NQF transfer case it is not equipped with a apply plate or apply plate bearing due to not having a internal clutch. If a noise is heard in a vehicle equipped with a NP1 or NQF transfer case see the operating guide lines below and compare to a like vehicle with similar mileage prior to attempting repairs.

The apply plate bearing designs in these transfer cases are not rated for continuous operation. They are intended for intermittent operation only when 4WD is required.

Long periods of continuous operation have been experienced in the U.S northern border states and in the provinces of Canada. This type of operation will shorten the life of the transfer case and in particular the apply plate bearing. As a general rule transfer case selector switches should be left in the 2HI mode unless road conditions dictate otherwise.

The following is a guideline for the proper use of 4WD in Magna transfer cases RPO's NP1, NP8, NQH and NQF.

1. 2HI mode sends all of the drive train torque to the rear wheels. This provides the most fuel efficient driving mode.
2. Auto/4WD mode when engaged constantly monitors the vehicle's drivetrain to provide optimum traction as road conditions dictate. Torque is automatically transferred to the front wheels to provide seamless 4WD operation. Auto mode is intended for on-road driving that includes rain, snow, ice and gravel.
3. 4HI provides enhanced traction for snow, ice, and gravel and most off road conditions. It is not intended for use on dry pavement.
4. 4LO provides enhanced traction and increased torque multiplication to handle extreme on and off road conditions such as steep hills, deep sand, mud, snow and ice. 4LO can also be used during boat launch operations for increased torque availability.

Note: 2-4 Not intended for continuous operation.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.