Mercedes-Benz bulletin LI35.31-P-074854
What it saysComplaint Noises from the rear axle differential, particularly when cornering slowly Cause Small quantity of water entering into oil of multiplate clutches at right and left Remedy Follow below steps to install vent… NHTSA’s full summary ↓
Mercedes-Benz filed this with NHTSA as a service bulletin dated Jan 23, 2026, received Jun 18, 2025, about the power train — 2 documents under this number. It names 15 model years (2020–2026). A service bulletin is not a safety recall: it is the manufacturer telling its dealers how to diagnose or repair a condition, and whether the work is paid for depends on the warranty in force. Quoting the number at a service desk can save a diagnosis.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationComplaint Noises from the rear axle differential, particularly when cornering slowly Cause Small quantity of water entering into oil of multiplate clutches at right and left Remedy Follow below steps to install vent hose A 177 350 02 03: (See attachment section for installation instructions with reference photos if needed) 1. Raise the vehicle with the vehicle lift 2. Detach the old breathers (2x) from the clutch housing right and left using a suitable tool (Figure 1) 3. Support rear axle differential 4. Remove the rear screw from the rear axle differential on the rear axle carrier (Figure 2) Note: pay attention to the position of the adjustment disc and mark it! 5. Lower rear axle differential 6. Clean the upper bore (Figure 6) on the left side of the rear axle carrier 7. Place the new vent hose with the Y-vent connector from right to left in front of the right rear axle shaft over the rear axle differential (Figure 3) 8. Slide the angle connectors onto the vent connections onto the rear axle differential on the left (Figure 4) and right (Figure 5) 9. Install the vent connection of the new line on the left side into the upper bore (Figure 6) of the rear axle carrier (Figure 7) 10. Attach the fastening clip (pre-assembled on the new bleed line) to the rear axle differential housing. (Figure 8) 11. Lift the rear axle differential and install the screw from the rear axle carrier (M14 torque 150 Nm) Note: pay attention to the position of the adjustment disc! Once new vent hose is installed: 1. Carry out oil change of clutch oil on left and right sides (Shell TF0870B). - DO NOT change the gear set oil (at center), since this is a long-life oil that is not related to the cause Return the vehicle to the customer and inform them that they must drive a distance of at least 250 km (155mi); The complaint should no longer occur.
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| LI35.31-P-074854 | Service bulletin | Jan 23, 2026 | 11027781 | PDF, 16,195 KB |
| LI35.31-P-074854 | Service bulletin | Jun 11, 2025 | 11019636 | PDF, 37 KB |
What the document itself lists
Part the bulletin names
| Part number | Description | Qty | Find it |
|---|---|---|---|
| A 000 989 4406 | CDNW | 11 | eBay Motors → |
Read by machine from the document NHTSA serves (2 pages), read Sep 30, 2026. A part number is shown only where it matches Mercedes-Benz’s own catalogue shape, an operation only with its code and time, and a description only where the reader got it whole; anything it could not settle is left out, and the PDF is the record. Times are the manufacturer’s warranty allowances, not a quote. Listings and prices on eBay Motors are the seller’s.
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The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5. One communication is usually filed as several documents — the bulletin, a dealer notice, an owner letter — and the number on any of them finds this page. A PDF link is shown only once NHTSA’s own server has been seen to serve that document; the rest are checked over the following nights. Quote the number at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themA vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
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What owners reported
Source: NHTSA complaint databaseOwners of the 15 model years this bulletin names have filed 146 complaints with NHTSA since 2015. 5 of them name Power Train — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.
A complaint is one owner’s account, not a defect finding, and a bulletin is not a recall. Nothing here says this bulletin was issued because of these complaints, or that the repair it describes fixed them. Complaint files on this site begin in 2015.
More bulletins about the power train
Source: same model, same component group34 other manufacturer communications filed against these Mercedes-Benz models under the same component group (power train), newest first. The eight newest are listed; the rest are on the Mercedes-Benz list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| LI27.00-P-073124 | Service bulletin | Sep 26, 2026 | Complaint Customer complaints relating to automatic transmission 725.0 (NAG3 Classic /9G‑TRONIC automatic transmission) and 725.1… |
| LI35.31-P-080353 | Service bulletin | Sep 14, 2026 | Complaint Whining / humming noises (described as foghorn‑like) from the drivetrain in the rear axle area during cornering. (figure 1) On the… |
| LI27.10-P-075869 | Service bulletin | Sep 14, 2026 | Complaint Only vehicles with a variable transfer case are affected. This can be identified through control unit N45 or N15/7 in the quick te… |
| LI 27.10-P-080851 | Service bulletin | Aug 29, 2026 | Complaint Intermittent shift feel or thud/clunk noise perceived, such as a brief jerk or transmission reaction during certain driving situat… |
| LI27.60-P-076554 | Service bulletin | Aug 26, 2026 | Complaint • Harsh 1‑2, 2‑3, and/or 3‑4 shift • Jerky shifting • Jolting when accelerating from stop Cause Insufficient software application… |
| LI27.19-P-080823 | Service bulletin | Aug 25, 2026 | Complaint Customers may report one or more of the following: • Transmission malfunction message • Check engine light illuminated • Shifts in… |
| PSL-NCU Return Parts 8/21 | Other | Aug 21, 2026 | Dear Mercedes-Benz USA Dealers, The part numbers listed in the chart below should no longer be installed, and any existing stock must be ret… |
| LI27.00-P-075630 | Service bulletin | Aug 5, 2026 | Complaint This document is intended as a pre-case diagnostic reference for transmission related concerns. It will also ensure that if a case… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Mercedes-Benz, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is Mercedes-Benz LI35.31-P-074854 a recall?
No. A service bulletin is a manufacturer communication filed with NHTSA under 49 CFR 579.5; a safety recall carries an NHTSA campaign number (two digits, a letter, six digits) and a federal duty to repair for free. Check the vehicle’s recalls by VIN at nhtsa.gov/recalls, or on its page here.
Is the LI35.31-P-074854 repair free?
Not automatically. A service bulletin describes how to diagnose or repair a condition; who pays depends on the warranty in force, any extension, and the dealer. Quoting the number can save a diagnosis either way. Every Mercedes-Benz warranty extension on file lists the ones Mercedes-Benz has filed.
Which vehicles does LI35.31-P-074854 cover?
The manufacturer filed it against 15 model years: 2026 Mercedes-Benz C-Class, 2025 Mercedes-Benz C-Class, 2024 Mercedes-Benz C-Class, 2023 Mercedes-Benz C-Class, 2026 Mercedes-Benz CLA-Class, 2024 Mercedes-Benz CLA-Class and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.