| Subject: | Whine Howl Noise From The Rear Differential On Vehicles Equipped With an 8.6 Rear Axle |
| Models: | 2006-2007 Cadillac Escalade, Escalade ESV, Escalade EXT |
| 2006-2007 Chevrolet Avalanche, Silverado Classic, Suburban, Tahoe |
| 2006-2007 GMC Sierra Classic, Yukon, Yukon Denali, Yukon XL |
| Equipped With a 8.6 Rear Axle |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Whine noise from the rear differential, most noticeable on coast between 40 to 55 mph in vehicles equipped with a 3.23 gear ratio (RPO GU5).
Note: The machining concern may be present and noticed in other gear ratios also but will be more prevalent in the 3.23 ratio.
Recommendation/Instructions:
Replaced the ring gear and pinion due to a possible machining concern that may cause a V type pattern or improper gear pattern see pictures below.
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.
