Mack service campaign S4533 202608
What it saysMack Trucks has determined that certain AN model trucks equipped with an MP8 Turbo Compound (TC) engine may experience TC Double Idler Gear failure due to incorrect bearing preload. NHTSA’s full summary ↓
Mack filed this with NHTSA as a service campaign dated Aug 5, 2026, received Sep 2, 2026, about the engine. It names 1 model year (2025). A service campaign is not a safety recall — there is no NHTSA campaign number and no federal requirement — but it is usually work the manufacturer pays for on the vehicles it names; the dealer checks the VIN against the manufacturer’s list.
What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationMack Trucks has determined that certain AN model trucks equipped with an MP8 Turbo Compound (TC) engine may experience TC Double Idler Gear failure due to incorrect bearing preload. TC units within this population are suspected to be affected, which could result in failure and potential engine damage. For the affected vehicle population, please follow the instructions provided below to remove the TC unit, replace the double idler gear with a new one, and reinstall the TC unit.
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| S4533 202608 | Service campaign | Aug 5, 2026 | 11036596 | PDF, 295 KB |
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 themAlso filed against: 2025 Mack Anthem (an).
None of these model years has a page on this site (it covers EPA-certified cars, trucks and SUVs from 2016), so the bulletin is listed here on its own.
More bulletins about the engine
Source: same model, same component group14 other manufacturer communications filed against the Mack Anthem (an) under the same component group (engine), newest first. The eight newest are listed; the rest are on the Mack list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| M0304 EC0033 202606 | Emissions | Jun 29, 2026 | Mack Trucks has determined that certain vehicles equipped with a model year (“MY”) 2017-2018 MP8 Turbo Compound (TC) engine may not meet Cal… |
| M0039 032026 | Emissions | Mar 2, 2026 | Emissions - EC0039 MST21 Failure to Detect P20EE - AN, CHU. |
| M0302 022026 | Emissions | Feb 1, 2026 | Emissions - Mack Trucks has determined that certain vehicles equipped with a model year (“MY”) 2017-2018 MP7 engine may not meet California… |
| S4533 072025 | Service campaign | Jul 1, 2025 | SC - Mack Trucks has determined that certain AN model trucks equipped with an MP8 Turbo Compound (TC) engine may experience TC Double Idler… |
| M0350 202504 | Emissions | Apr 2, 2025 | ER - Mack Trucks has identified that the Selective Catalyst Reduction (SCR) system in certain vehicles equipped with the MY 2017 or 2018 MP8… |
| M0311 202410 | Emissions | Oct 25, 2024 | EMISSION RECALL - SCR Replacement |
| M0310 202410 | Emissions | Oct 25, 2024 | EMISISON RECALL - SCR Replacement. |
| M0296 202410 | Emissions | Oct 1, 2024 | Emission Recall - Mack Trucks has determined that certain vehicles equipped with a model year (“MY”) 2022-2024 MP8 model engines, may be equ… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Mack, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is Mack S4533 202608 a recall?
No. A service campaign 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.
Is the S4533 202608 repair free?
A service campaign is usually paid by the manufacturer on the vehicles it names, within the terms and time limit the document sets; the dealer checks the VIN against the manufacturer’s list.
Which vehicles does S4533 202608 cover?
The manufacturer filed it against 1 model year: 2025 Mack Anthem (an). Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.