2021 Mercedes-Benz AMG GT Clunking Noise TSB

Symptoms

Owners of the 2021 Mercedes-Benz AMG GT may experience a distinct "throttle lift-off clunking noise from the side shaft when moving off (audible at the outboard end)." This clunking sound is typically heard once when changing from forward to reverse gears, and vice versa. This issue can also manifest as general cracking, knocking, or banging noises related to the power transmission, drive shaft, axle shaft, or front axle chassis/suspension. The TSB categorizes these symptoms under:

• Chassis/suspension > Noises > Cracking
• Power transmission > Noises > Throttle lift-off clunking noise
• Power transmission > Drive shaft > Axle shaft > Noises > Knocking/banging
• Chassis/suspension > Axle > Front axle > Noises > Cracking

A sound file, "Beanstandung Lastwechselknacken.mp3", is referenced in the TSB as an attachment to help technicians identify the sound.

Cause

The root cause of the Mercedes-Benz AMG GT clunking noise is identified as micromovement occurring in the connection between the wheel bearing inner race and the joint housing of the side shaft. This slight movement leads to the audible clunk. Technicians can confirm this by experimentally loosening the outboard collar nut by one turn; if the noise is eliminated, the micromovement is the problem.

Important Notes for Repair

When performing this repair, technicians must adhere to specific guidelines:

• The collar nut must always be replaced after being loosened and must be tightened to the specified torque.
• Before using the antifriction coating (Molykote), it must be stirred or shaken thoroughly for at least one minute to ensure proper application.

Repair Procedure Summary

The repair involves applying a specialized low-friction paint, Molykote, to the contact surface of the side shaft and wheel bearing. The procedure is as follows:

1. Remove Side Shafts: The outboard side shafts must be removed from the vehicle. This step includes extracting the outer joint gearing from the wheel hub.
2. Clean Contact Surface: A specific contact surface, labeled 'A' in the technical document's images (e.g., "Outer joint housing before"), on the outer joint housing must be thoroughly cleaned. This cleaning should be performed using "spirit" to ensure the surface is free of dust and grease.
3. Coat Contact Surface: After cleaning, contact surface A (as shown in images like "Outer joint housing after") is coated with Molykote paint. The coated part must then be left to dry for one hour while still removed from the vehicle.
4. Reinstall Side Shafts: Once the Molykote paint has dried, the side shafts are reinstalled into the vehicle.

Required Parts

The following part is required for this repair:

Part number	Designation	Quantity
A0009890152 10	Low-friction paint (Molykote)	1

Operation Codes for Technicians

For warranty and repair documentation, the following operation numbers and damage codes apply:

Op. no.	Operation text	Damage code	Note
330000	REMOVE/INSTALL PARTS OF LEFT FRONT AXLE SHAFT.	33H1034	Left side shaft
330000	REMOVE/INSTALL PARTS OF RIGHT FRONT AXLE SHAFT.	33W1034	Right side shaft
330000	REMOVE/INSTALL PARTS OF FRONT AXLE SHAFTS (BOTH)		Left and right side shafts

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Source: NHTSA ID: 11019018, TSB ID: L133.30-P-056665