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Technical Service Bulletin

39 Gearbox: noises/vibrations in tight bends - A8. Q7, and Q8 models

United States 444 Volkswagen of America, Inc. (6444)

[Status | Released for publishing

Release date Jun 20, 2025

New customer code

Object of complaint Complaint type [Position]
transmission -> power distribution, transmission of power -> transmission of functionality ->
power -> transfer case transmission of power irregular

entire vehicle -> driving performance, consumption -> acceleration nies. viratons-> [|
chassis -> steering, steering assist -> steer noises, vibrations ->

rubbing

Vehicle data

A8

Sales types

aorta |

aoa |

aoa |

aoa |

asa |

aja fT

A8

Sales types

aoa |

aja fT

area |

anja fe

Final drive code
aoa |
aoja |
Q7, Q8

Sales types

Final drive code
aja fT
aoa fT
aoa |
aoa |
aoa |
aoa |
aoa fo
aoa fT
aorja fT
Q7

Sales types

aja fT
aoosfa fT
anja fo
aoa PR
Documents

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Technical Service Bulletin Transaction No.: 2074857/2

39 Gearbox: noises/vibrations in tight bends - A8. Q7, and Q8 models Release date: Jun 20, 2025

Condition

REVISION HISTORY

[revision [pate [purpose

2» |. | Revised title (Updated to include Q8)

08/30/2024 | Initial publication

Customer states:

Noises/vibrations in tight bends.

Workshop findings:

The complaint can be reproduced. Compared with an identical comparison vehicle (especially tire size and tire

manufacturer), the complaint on the affected vehicle under identical conditions is significantly more noticeable.

Technical Background

General information on all-wheel drive with self-locking center differential

The self-locking center differential is used in different gearboxes. The self-locking effect is generated using worm

gears. This design is characterized by a high locking effect. In conditions where the front and rear axle have different

grip levels, the axle that has more traction is able to provide up to three times more torque than the other axle.

With the Torsen differential, Audi has a permanent all-wheel drive system that provides superior driving dynamics to

many other switchable systems as it does not require any time to regulate the power, thereby avoiding delayed

responses. However, if there is a significant speed difference between the front and rear axles in very tight bends

and the vehicle is travelling at a high speed, the friction forces between the flanks of the worm gear and the axial

thrust washers in the differential are extremely high. Under these conditions, a stick-slip effect can occur when the

two surfaces contact each other. This can cause other components in the vehicle to resonate and generate a

vibration or hum (secondary effects).

This issue is merely a comfort-related complaint. The specified behavior is construction-related. No damage

occurs to components.

Please also note that there are other factors which can have a negative effect:

+ Wheels: different tread depth, hardness, width, summer or winter wheels, different tire manufacturers (AO
code)

+ Additional tension in the drive train due to wheel alignment

+ Possible noise transmission from assembly mountings

+ Possible noise generation/increase due to loose parts, parts under tension or incorrectly installed parts in the
interior of the vehicle or the chassis.

Production Solution

Not applicable.

Service

It may be possible to achieve an improvement by changing the gear oil in the transfer box. Please note the
precise approach as specified in the Workshop Manual.
The degradation of the friction modifier in the oil can result in a more pronounced stick-slip effect with increased
mileage. Replacing the gear oil in the transfer box also replaces the friction modifier and the issue will be
significantly reduced within 125 miles of replacement (depending on the driving profile).
Evaluation requires the gearbox oil to be between 40° C and 70° C (104° F and 158° F). Regarding this
complaint, higher and lower temperatures are not irregular. The workshop tester should therefore be used to
determine the exact gearbox oil temperature.
The full effect of the oil change only becomes apparent after driving a distance of approx. 60 miles.
Warranty
Claim Type: + Ifthe vehicle is outside of any warranty, this Technical Service Bulletin is
informational only.
Damage Code: 0020
Labor Operations: Remove and install rear transmission mount 3738 19xx See SRT with
associated operations
Replace gear oil 3990 5599 50 TU
Diagnostic Time: GFF 0150 0060 Labor according to the
diagnostic log
Charge battery 2706 8950 See SRT with
associated operations
Extended road test after measure 0121 0199 According to punch
time
(Max 200 TU)
Claim Comment: As per TSB 2074857/2
All warranty claims submitted for payment must be in accordance with the Audi Warranty Policies and Procedures
Manual. Claims are subject to review or audit by Audi Warranty.
Additional Information
All part and service references provided in this TSB (2074857) are subject to change and/or removal. Always check
with your Parts Department and/or ETKA for the latest information and parts bulletins. Please check the Repair
Manual for fasteners, bolts, nuts, and screws that require replacement during the repair.
©2025 Audi of America, Inc. All rights reserved. The information contained in this document is based on the latest
information available at the time of printing and is subject to the copyright and other intellectual property rights of
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