2021 Audi Rear Differential Oil Leak TSB

Audi Technical Service Bulletin (TSB) 2064024/3, revised on February 6, 2023, addresses an oil leak issue originating from the rear final drive's sport differential. This bulletin supersedes a previous version, TSB 39 22 47, dated April 29, 2022, and was initially published on August 26, 2021.

This TSB specifically applies to various 2021 Audi models equipped with a V8 engine and Sports Differential. Owners of affected vehicles may observe an Audi rear differential oil leak from the rear of their vehicle.

Symptoms

Owners may notice an oil leak from the rear of the vehicle. Upon inspection, technicians will typically confirm an oil leak from the top of the differential near the output flanges. The root cause is often that one or both of the sealing caps are missing from the pressure limiting valves on the differential.

Important Warnings for Owners and Technicians

This Technical Service Bulletin 2064024/3 includes several critical warnings to ensure a proper and safe repair:

• "The clutch valves can be damaged if subjected to impact." Ensure the differential is handled carefully during removal and placement.
• "The bolt head on the pressure limiting valve (hexagon socket head bolt in the hole) must not be turned." This prevents damage to the valve itself.
• "Chemical agents (brake clean etc.) must not enter the system. Do not let chemical agents get into the exposed pressure limiting valve." Only use approved cleaning methods.
• "Steps 3 to 7 must be performed within 5 minutes (due to hardening of locking fluid)." This emphasizes the time-sensitive nature of installing the sealing caps.
• "It is not permitted to remove a sealing cap that has already been installed." Only missing caps should be replaced; existing caps should not be disturbed.

Repair Procedure Summary

The repair for the Audi rear differential oil leak involves a multi-step process to address the missing sealing caps:

1. The rear differential is removed from the vehicle following Elsa Repair Manual instructions and placed on a suitable working surface, ensuring the clutch valves are protected from impact.
2. The area around the pressure limiting valve (where the sealing cap is missing) is thoroughly cleaned with a clean cloth. If only one cap is missing, the existing cap is not removed.
3. A new sealing cap is placed on a drift and coated with locking fluid (D 154 100 A1) around its outside edge.
4. The sealing cap is then carefully knocked onto the pressure limiting valve using the drift and a soft-faced hammer until it seats correctly, indicated by a dull sound and spring-back effect.
5. Any excess locking fluid is removed.
6. A visual check confirms the sealing cap is installed evenly.
7. A caliper gauge is used to measure the installation depth of the sealing cap in three locations, ensuring it meets specifications (minimum 1.00 mm, deviation no more than 0.3 mm).
8. If both sealing caps were missing, steps 3-7 are repeated for the second cap.
9. After a 30-minute drying time, the area around both sealing caps is cleaned again.
10. Silicone adhesive sealant (D 176 501 A1) is applied over the entire surface of both sealing caps to bond them securely. A minimum 30-minute drying time is required before reinstallation.
11. The differential is reinstalled into the vehicle, taking care not to disturb the still-hardening silicone sealant.
12. The ATF level of the differential is checked and topped up as needed.

Required Parts and Tools

To perform the repair described in TSB 2064024/3, the following parts are required:

Part Number	Part Description	Quantity
0BX 598 080	Repair kit for sealing cap	01
D 154 100 A1	Locking fluid 10ml	01
N 90281802	Seal Bolt with seal ring	01
D 176 501 A1	Silicone adhesive sealant 50ml	0.5

Warranty Information

Warranty claims for this repair are processed under specific guidelines:

• Claim Type: 110 for vehicles up to 48 months/50,000 miles, or G10 for CPO Covered Vehicles (owner verification required).
• If the vehicle is outside warranty, this Technical Service Bulletin is for informational purposes only.
• Service Number: 3989
• Damage Code: 0050
• Labor Operations: Remove and install rear final drive (3988 19XX), with associated operations as per the Service Repair Time (SRT).

All warranty claims must comply with the Audi Warranty Policies and Procedures Manual and are subject to review by Audi Warranty.

Revision History

• Revision 3 (February 6, 2023): Revised Warranty information, adding GFF (Goodwill Factor).
• Revision 2 (April 29, 2022): Revised Header to include S4, S5, RS5, and SQ5 models.
• Revision 1 (August 26, 2021): Initial publication of the Technical Service Bulletin.

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Source: NHTSA ID: 10231562