Howling, Whining/Whirring, Shudder/Vibration, and/or Grinding Noise While in 4HI, 4HI Auto and/or During Parking Lot Maneuvers in Auto Mode – 2014-2021 Cadillac Chevrolet GMC

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Service Bulletin Bulletin No.: 19-NA-136
Date: December, 2020
TECHNICAL
Subject: Howling, Whining/Whirring, Shudder/Vibration, and/or Grinding Noise While in 4HI, 4HI
Auto and/or During Parking Lot Maneuvers in Auto Mode
Brand: Model:
Model Year: VIN:
Engine: Transmission:
from to from to
Cadillac Escalade 2015 2019
Chevrolet
Colorado 2015 2021
Silverado 2014 2018
Silverado 1500
(New Model – 12th
VIN Digit = 7) – 4WD
2019 2019
Silverado 1500
(New Model) 2019 2019
Silverado 1500 2020 2021
Silverado
2500HD/3500HD 2019 2021
Silverado LD 2019 2019
Suburban 2015 2019
Tahoe 2015 2019
GMC
Canyon 2015 2021
Sierra 2014 2018
Sierra 1500
(New Model) 2019 2019
Sierra 1500 2020 2021
Sierra
2500HD/3500HD 2019 2021
Sierra Limited 2019 2019
Yukon 2015 2019
Involved Region or Country North America
Additional Options (RPOs) NP0, NQ6, NQ7, NQF, NQG, NQH
Condition
Some customers may comment on one or more of the following conditions during parking
lot maneuvers in AUTO Mode or highway speeds in 4HI or Auto:
• Howling noise
• Whining/Whirring noise
• Shudder/Vibration
• Grinding noise
Some customers also may state that a noise can be heard in 4HI, but goes away when
switched to 2HI.
Some technicians may find the concern coming from the transfer case.
Page 2 December, 2020 Bulletin No.: 19-NA-136
Cause
This condition may be caused by normal transfer case clutch plate break in and wear,
creating excess contaminants in the fluid.
⇒ This may result in a customer complaint of excessive noise present with
4WD engaged and goes away when switched back to 2WD.
Correction
Perform road test to diagnose transfer case noise:
1. Place vehicle into AUTO mode, and perform low speed parking lot maneuvers,
listening for the noise description noted above.
2. Place vehicle in 4HI. From a stop under moderate acceleration, listen for any
growling, howling, whining or whirring noise.
Note: This video audio was recorded by using a picoscope microphone and was
provided as an example for what to listen for. The growling/howling/whirring noise can be
heard in the vehicle cabin during moderate acceleration in 4HI from a stop, or during
steady speed switching between 2HI and 4HI as shown in the video.
3. As shown in the video above, at approximately highway speeds (55 mph or 89 km/
h) toggle between 4HI and 2HI, and listen for the same noise description noted
(Growling, etc.).
Once the transfer case noise is confirmed, refer to Transfer Case Fluid Replacement
in SI.
Parts Information
Causal
Part
Description Part
Number
Qty
N/A Fluid 88865601
(in Canada
19420142)
Refer to
Fluid
Capacities
in SI
Warranty Information
For vehicles repaired under the Powertrain coverage,
use the following labor operation. Reference the
Applicable Warranties section of Investigate Vehicle
History (IVH) for coverage information.
Labor Operation Description Labor Time
3080368* Diagnostic Test and Test Drive 0.5 hr
Add Fluid Drain and Fill 0.3 hr
*This is a unique Labor Operation for Bulletin use only.
Version 2
Modified
Released June 19, 2019
Revised November 30, 2020 – Added Addition Vehicles to the Model section and
Additional Transfercase RPOs to the Additional Options (RPOs) section.

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