Noise, Vibration, and/or Harshness Issues/Clunk Noise Heard During Coast Down Event – 2020-2021 Chevrolet Silverado & GMC Sierra 2500HD/3500HD

NHTSA ID Number: 10198888

Manufacturer Communication Number: 21NA120

 

Summary

This technical bulletin provides the tech with a procedure to check if the transmission is the cause of the concern by checking the data.

 

 


4 Affected Products

Vehicles

MAKE MODEL YEAR
CHEVROLET SILVERADO 2500 2020-2021
GMC SIERRA 2500 2020-2021

 


Condition

Some technicians or customers may comment on one or more of the following conditions after the transfer case was removed from the transmission and reinstalled during a recent repair:

• Harsh downshift during a coast down event

• Noise during a coast down event

• Vibration during a coast down event

• Harshness issues such as a clunk noise heard during coast down event

 

Cause

This condition may be caused by a misalignment between the transmission output shaft and the transfer case input.

Transfer case to transmission misalignment could cause the transfer case shift collar to slip out of engagement.

 

Correction

1. Connect the GDS Scan Tool and monitor transmission shift data.

2. Drive the vehicle and duplicate the condition while monitoring transmission shift data to determine if the noise/clunk/roughness occurs during the downshift or if the noise/clunk/roughness occurs randomly during the de-acceleration event.

⇒ If it is determined that the noise/clunk/roughness does not occur at a transmission downshift, shift point follow published Service Information for Transfer Case Assembly Replacement (with MGM MGU Automatic Transmission)

Note: The transfer case does not need to be completely removed from the vehicle. The attaching bolts must be loosened (not removed) to allow the transfer case to be separated from the transmission a minimum of a ½ (13mm) but no more than 1 inch (25mm). The use of transmission jack or adjustable jack stand may provide support in holding the transfer case to the transmission. Proper transfer case to transmission bolt installation, tightening sequence and proper torque must be followed.

If the noise/clunk/roughness is occurring during a transmission downshift, shift point, refer to SI for further diagnostics.

 


 

 


1 Associated Document

Manufacturer Communications

Bulletin No.: 21-NA-120
Date: May, 2021

https://www.nhtsa.gov/recalls?nhtsaId=10198888

MC-10198888-9999.pdf 1684.294KB

MC-10198888-9999

 


 

Bestseller No. 1
Mobil 1 Full Synthetic LV Automatic Transmission Fluid HP, 6-Pack of 1 quarts
  • Mobil 1 Synthetic LV ATF HP is a high performance synthetic automatic transmission fluid that delivers extended transmission life with improved thermal stability
  • Has outstanding long-term frictional properties to help improve and extend transmission efficiency, smooth shifting performance, and fuel economy
  • Exceptional thermal and oxidation stability keep transmissions clean to help provide outstanding performance even under severe driving conditions
  • Helps provide reliable lubrication at temperatures down to -78F (-61C), and supports viscosity retention under the most severe high-temperature operating conditions
  • Recommended for use in modern high-performance vehicles requiring Dexron HP ATF
SaleBestseller No. 2
Valvoline MaxLife ATF Multi-Vehicle Full Synthetic Automatic Transmission Fluid 1 GA
  • FOR USE IN 95% of ATF VEHICLES INCLUDING MOST CVTs in operation with US registered light duty applications
  • HIGH PERFORMANCE CONDITIONING AGENTS prolong seal elasticity to prevent leaks
  • IMPROVE DURABILITY & TRANSMISSION LIFE with anti-wear technology to avoid costly repairs
  • ENHANCED HIGH & LOW TEMP PERFORMANCE supports transmission fluid in all weather situations
  • FULL SYNTHETIC FORMULA protects against engine breakdown better than conventional fluids
Bestseller No. 3
Ford XT-10-QLVC 5 Quart Mercon-Lv Automatic Transmission Fluid 1 Pack
  • Ford XT-10-QLVC 5 Quart Mercon-Lv Automatic Transmission Fluid 1 Pack
  • -Make sure this fits by entering your model number. -Geniune OEM part
  • Geniune Ford replacement parts are a part of what keeps a vehicle looking and performing its best over the long term, something that the Ford company has always known. When choosing parts for your Ford vehicle, make the best choice: Use durable and affordable parts made specifically for the manufacturer of your vehicle. These genuine Ford parts are a fit for your vehicle. Ford OEM parts are the way to go if you want to keep your vehicle as close to its original condition as possible.
Bestseller No. 4
Mobil 1 Synthetic LV ATF HP Case 6 x 1 Quart
  • Mobil 1 Synthetic LV ATF HP Case 6 x 1 Quart
  • Applications-Mobil 1 Synthetic LV ATF HP is recommended for use in modern high performance vehicles requiring DEXRON HP ATF DEXRON license code J-62120
Bestseller No. 5
ACDelco GM Original Equipment 10-9244 Dexron VI Full Synthetic Automatic Transmission Fluid - 1 gal
  • Backward compatible with previous DEXRON automatic transmission fluids and can be used as a much-improved replacement for older vehicles/transmissions originally using previous DEXRON fluids
  • Improved performance over previous DEXRON fluids in: friction durability, viscosity stability, aeration and foam control, and oxidation resistance.
  • Designed for anti-wear protection and shear stability
  • Some ACDelco GM Original Equipment parts may have formerly appeared as GM Genuine Parts (OE) or ACDelco Professional
  • ACDelco GM Original Equipment parts are designed, engineered and tested to rigorous standards, and are backed by General Motors
SaleBestseller No. 6
Royal Purple 06320-6PK Max ATF High Performance Synthetic Automatic Transmission Fluid - 1 qt. (Case of 6)
  • High Film Strength Helps to Dramatically Reduce Heat and Wear
  • Automatic Transmissions Generate a Great Deal of Heat and Depend on Transmission Fluid for Cooling and Protection
  • Significantly Reduces Heat to Extend the Life of Your Transmission
  • Fully Compatible and Can Be Mixed with Other Automatic Transmission Fluids
  • Recommended for Multiple Passenger Vehicles
SaleBestseller No. 7
Mobil 1 112980 Synthetic Automatic Transmission Fluid - 1 Quart (Pack of 6)
  • Material code - 98KY58
  • Helps improve and extend transmission efficiency, smooth shifting performance and fuel economy
  • Keeps transmissions clean to help provide outstanding performance even under severe driving conditions
  • Significant wear protection which can contribute to long transmission life
  • Helps to provide prompt and reliable lubrication at ambient temperatures down to -54 degrees Celsius
Bestseller No. 8
SaleBestseller No. 9
Idemitsu ATF Type TLS-LV (WS) Automatic Transmission Fluid for Toyota, Lexus, Scion - 5QT
  • Optimized viscosity and advanced friction reducing additive technology provide exceptional fuel economy performance
  • Precisely engineered frictional characteristics guarantee smooth shifting and outstanding anti-shudder performance
  • Excellent resistance to oxidation and thermal breakdown provide long fluid life and extended protection
  • Provides superior deposit control and protects metal surfaces from rust and corrosion
  • Exceptional wear protection of gears and bearings
Bestseller No. 10
Schaeffer Manufacturing Co. 0205A-012 Dexron VI/MERCON LV Automatic Transmission Fluid, 1-Quart Bottle (Pack of 12)
  • Anti-wear protection for clutches, gears and pumps
  • Smoother and quieter shifting
  • Rust and corrosion protection
  • Proper friction control for long life performance and smooth lock ups

Last update on 2023-05-13 / Affiliate links / Images from Amazon Product Advertising API

This product was presentation was made with AAWP plugin.

Leave a Comment

Share to...