Brakes - Vibration/Rumble On Downhill Braking
TECHNICALBulletin No.: 10-05-23-001C
Date: October 29, 2012
Subject: Brake Induced Pulsation/Vibration Felt in Steering Wheel, Rumble Noise from Underbody During Downhill Descent (Verify Condition and Replace Front Brake Pads)
Models:
2008 Chevrolet Silverado Light Duty (LD)
2008 GMC Sierra Light Duty (LD)
2nd-Design Only - w/ Pad Spreading Spring Clips (Refer to PIT4611 for Design Identification)
Equipped with Disc/Drum Brakes (RPO JF3) and Stabilitrak (RPO JL4)
2009-2013 Chevrolet Silverado Light Duty (LD)
2009-2013 GMC Sierra Light Duty (LD)
Equipped with Disc/Drum Brakes (RPO JF3 or JF7) and Stabilitrak (RPO JL4)
Supercede:
This bulletin is being revised to add the 2013 model year. Please discard Corporate Bulletin Number 10-05-23-001B (Section 05 - Brakes).
Condition
Some customers may comment on a pulsation or vibration mostly concentrated in the steering wheel during downhill descent as specifically described. This condition will most often begin as an increasing rumbling noise coming from the underbody or the front of the vehicle. This condition is exhibited mostly in mountainous regions.
Note
Use care to ensure the following diagnosis and repair are only attempted if the conditions and concern match those listed, and if the concern can be duplicated under the same conditions.
This condition occurs ONLY under the following conditions:
- When the vehicle is driven as follows:
- On a downhill descent on a fairly steep grade (approximately 5% or greater).
- On taller hills (roughly 1.5 km [1 mi] road length or greater), without sharp turns.
- At speeds above 64 km/h (40 mph).
- Using the brakes just enough to maintain the speed limit when moving downhill.
- Typically, a rumbling noise will be heard first, building in intensity, followed by increasing pulsation, or vibration, felt in the steering wheel, then typically felt in the floor panel.
- The condition will be eliminated once the vehicle is driven on relatively flat ground, typically for 1.5-3 km (1-2 mi).
Cause
This condition may be caused by interaction between the front brake lining material and the front brake rotors.
Correction
Important
DO NOT attempt any repairs on the vehicle until you verify the specific condition is present by following the steps below:
1. Warm up the vehicle by driving approximately 8 km (5 mi).
2. Drive the vehicle in the lane closest to the side of the fairly steep grade (roughly 5 percent or greater), taller hill (roughly 1.5 km [1 mi] road length or greater), without sharp turns, and with a speed limit of 64 km/h (40 mph) or greater, with the side windows down.
3. While in Drive, descending downhill, apply the brakes naturally, only as needed, to maintain the speed limit.
4. Observe for noise, followed by pulsation/vibration. Observe where the noise, pulsation and/or vibration are most noticeable.
5. Drive the vehicle on relatively flat ground for 1.5-3 km (1-2 mi) to verify that the condition goes away completely.
Note
If the Front Pad Kit listed is used to correct any condition other than the condition described in this bulletin, the vehicle could experience higher mileage corrosion-induced brake pulsation.
If the condition described HAS NOT been verified, or if the condition observed IS NOT most noticeable through the steering wheel, the observed condition may have a different cause, such as a tire/wheel or rear brake issue, etc. Refer to SI for any further related diagnostics.
If the condition described has been verified, and if the condition is most noticeable through the steering wheel, and if the condition was eliminated after driving the vehicle on relatively flat ground, typically for 1.5-3 km (1-2 mi), perform the following inspections and repairs.
Important
- It is critical to use the proper OEM brake rotors. Use of Non-OEM rotors may prevent the condition from being corrected long term.
- If Non-OEM rotors are identified, these rotors are NOT covered under the GM New Vehicle Limited Warranty.
1. Inspect the front brake rotors to ensure that they are OEM rotors.
- Remove the brake rotor from the vehicle.
- Inspect the back side of the rotor for the Bosch Logo. If the Bosch logo IS NOT present, replace with OEM GM rotors, P/N 25819670.
2. Inspect the front brake rotors for Assembled Lateral Runout (LRO) and thickness variation. Follow SI procedures.
3. Inspect the front brake rotors for minimum thickness. Follow SI procedures.
4. If the rotors are within specifications, DO NOT refinish or replace the rotors.
5. If the rotors are out of specifications, refinish the rotors on a qualified lathe, or replace the rotors as appropriate. Follow SI procedures.
Note
To prevent a noise concern, follow the brake pad insulator preparation and seating instructions as referenced in Front Brake Pad Replacement (1500) in SI.
6. Install the specified front pad kit, GM P/N 25910432. Follow SI procedures.
7. Ensure that the condition has been eliminated under the same conditions.
Parts Information
Warranty Information
For vehicles repaired under warranty, use:
Note
H9745 includes time for road testing and for removal of 1 rotor to inspect for OEM markings.
Disclaimer