Subject: | Bearing or Metallic Grinding Sound While Operating In Auto, 4HI or 4LO Modes |
Models: | 2007-2009 Chevrolet Avalanche, Silverado, Suburban, Tahoe |
2007 Chevrolet Silverado Classic |
2007-2009 GMC Sierra, Sierra Denali, Yukon, Yukon XL, Yukon XL Denali |
2007 GMC Sierra Classic |
Equipped with Magna Transfer Case RPO NP1, NP8, NQF, NQH |
This Pi was superceded to add model years. Please discard PIP4146.
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.
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 electric shift transfer cases RPO's NP1, NP8, NQH and NQF.
** 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.