28 Belt drive parts are listed for the 2021 Audi S4, in 3 part types, covering both the 3.0L V6 Supercharged and the 3.0L V6 Turbocharged. Each one has a brand, a manufacturer part number and notes that say where it fits.
The belt drive system on the 2021 Audi S4 spins the accessories — serpentine and V-belts, tensioners, idlers and pulleys. All 28 listed parts are Belt (17 parts), Idler Pulley (10 parts) and Belt Tensioner (1 part).
The 2021 Audi S4 was sold with both the 3.0L V6 Supercharged and the 3.0L V6 Turbocharged. 18 parts fit every engine; the other 10 are engine-specific. Each part shows which engine(s) it fits.
The most listed brands for 2021 Audi S4 belt drive parts are CONTINENTAL (9 parts), GATES (4 parts) and DAYCO (4 parts), plus 6 more brands. Quality grades include Standard Replacement and Economy.
6 parts on this 2021 Audi S4 page carry a "Popular" badge — the source catalog's flag for options frequently chosen for this vehicle — including CONTINENTAL 440K4MK (Belt) and CONTINENTAL 50100 (Idler Pulley). Click any part number to see every vehicle that part fits.
Belt
Economy
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| CONTINENTAL Popular Fits: all 2021 S4 engines | 440K4MK | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Mileage MakerSerpentine | View on Amazon |
| GATES Popular Fits: all 2021 S4 engines | K060465 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Micro-V | View on Amazon |
| DAYCO Fits: all 2021 S4 engines | 5040440DR | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Drive Rite®Serpentine | View on Amazon |
| DAYCO Fits: all 2021 S4 engines | 5060463DR | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Drive Rite®Serpentine | View on Amazon |
| FVP Fits: all 2021 S4 engines | 440K4 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Multi V-BeltSerpentine | View on Amazon |
| GATES Fits: all 2021 S4 engines | K040440 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Micro-V | View on Amazon |
| ROADMAX Fits: all 2021 S4 engines | 4K440AP | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | V-RibbedSerpentine | View on Amazon |
| ROADMAX Fits: all 2021 S4 engines | 6K465AP | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | V-RibbedSerpentine | View on Amazon |
Standard Replacement
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| CONTINENTAL Popular Fits: all 2021 S4 engines | 4040440 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Multi V-BeltSerpentine | View on Amazon |
| DAYCO Popular Fits: all 2021 S4 engines | 5060463 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Serpentine | View on Amazon |
| ACDELCO Fits: all 2021 S4 engines | 4K440 | 🇺🇸 US 🇨🇦 CA | Professional / GoldSerpentine | View on Amazon |
| ACDELCO Fits: all 2021 S4 engines | 6K465 | 🇺🇸 US 🇨🇦 CA | Professional / GoldSerpentine | View on Amazon |
| BANDO Fits: all 2021 S4 engines | 4PK1120 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Rib Quantity: 4 | View on Amazon |
| BANDO Fits: all 2021 S4 engines | 6PK1180 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Rib Quantity: 6 | View on Amazon |
| CONTINENTAL Fits: all 2021 S4 engines | 4060462 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Multi V-BeltSerpentine | View on Amazon |
| CONTINENTAL Fits: all 2021 S4 engines | 4PK1120 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Metric LineSerpentine | View on Amazon |
| DAYCO Fits: all 2021 S4 engines | 5040440 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Serpentine | View on Amazon |
This table covers the serpentine and accessory belts that drive the front accessories. Typical signs include squeal on cold start, cracks across the ribs, or glazing on the back of the belt. A new belt on a worn tensioner will squeal within weeks — spin the idlers by hand while the belt is off.
17 Belt parts are listed for the 2021 Audi S4, from CONTINENTAL, DAYCO, GATES and 4 other brands. CONTINENTAL 440K4MK carries the "Popular" badge. All of them fit every engine offered in the 2021 S4.
In the Economy grade, GATES, DAYCO, ROADMAX and 2 other brands supply 8 parts: the catalog's value-priced group. A representative part number is CONTINENTAL 440K4MK.
The Standard Replacement section lists 9 options from CONTINENTAL, DAYCO, ACDELCO and 1 other brand — built to original-equipment specification. CONTINENTAL 4040440 is listed in this group.
Belt Tensioner
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| CONTINENTAL Fits: all 2021 S4 engines | 49879 | 🇺🇸 US 🇨🇦 CA 🇲🇽 MX | Multi-V | View on Amazon |
This table covers the automatic tensioners that hold belt tension. Typical signs include belt flutter, a chirp that returns after a new belt, or a damper that no longer holds the arm. Replace the tensioner with the belt at higher mileage; the labor overlaps almost entirely.
This group shows a single part: CONTINENTAL 49879.
Idler Pulley
Economy
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| VAICO Fits: 3.0L V6 Turbocharged | V108920 | 🇺🇸 US | View on Amazon | |
| VAICO Fits: 3.0L V6 Turbocharged | V108921 | 🇺🇸 US | View on Amazon |
Standard Replacement
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| CONTINENTAL Popular Fits: 3.0L V6 Turbocharged | 50100 | 🇺🇸 US 🇨🇦 CA | Smooth | View on Amazon |
| LITENS Popular Fits: 3.0L V6 Turbocharged | 900699A | 🇺🇸 US 🇨🇦 CA | Smooth | View on Amazon |
| CONTINENTAL Fits: 3.0L V6 Turbocharged | 50099 | 🇺🇸 US 🇨🇦 CA | Smooth | View on Amazon |
| GATES Fits: 3.0L V6 Turbocharged | 36901 | 🇺🇸 US 🇨🇦 CA | Smooth | View on Amazon |
| Brand | Part Number | Markets | Notes | Buy |
|---|---|---|---|---|
| CONTINENTAL Fits: 3.0L V6 Supercharged | 50099 | 🇲🇽 MX | Smooth | View on Amazon |
| CONTINENTAL Fits: 3.0L V6 Supercharged | 50100 | 🇲🇽 MX | Smooth | View on Amazon |
| GATES Fits: 3.0L V6 Supercharged | 36901 | 🇲🇽 MX | Smooth | View on Amazon |
| LITENS Fits: 3.0L V6 Supercharged | 900699A | 🇲🇽 MX | Smooth | View on Amazon |
This table covers the idler pulleys the belt wraps around. Typical signs include a chirp that follows engine speed, or a pulley that feels rough or has play. Replace a noisy idler with the belt — the labor is already paid for.
10 Idler Pulley parts are listed for the 2021 Audi S4, from CONTINENTAL, VAICO, LITENS and 1 other brand. CONTINENTAL 50100 carries the "Popular" badge.
Economy: 2 parts, from VAICO. A representative part number is VAICO V108920.
The Standard Replacement section: 4 options from CONTINENTAL, LITENS and GATES. CONTINENTAL 50100 is listed in this group.
4 ungrouped parts are not assigned to a grade, with the same engine-level match.
Buying Belt Drive Parts for a 2021 Audi S4
On this vehicle, the belt drive system spins the accessories — serpentine and V-belts, tensioners, idlers and pulleys.
- Match the engine first. Some belt drive parts fit every engine; others are engine-specific. Each row shows which engine(s) it fits.
- Read the notes on each row for position, trim and spec qualifiers before you order.
- Where labor overlaps, replace the tensioner and idler pulleys with any belt at higher mileage — the labor overlaps almost entirely.
- Cross-reference the manufacturer part number against your old part or a service-manual listing.
Start with the largest groups on this page: Belt and Idler Pulley .
Frequently Asked Questions
How many belt drive parts fit the 2021 Audi S4?
Our catalog currently lists 28 belt drive parts for the 2021 Audi S4 across 3 subcategories and 9 brands, covering both the 3.0L V6 Supercharged and the 3.0L V6 Turbocharged. Each part is matched to the engine(s) it fits.
Do belt drive parts differ between 2021 Audi S4 engines?
Some do. 18 parts fit every engine; the other 10 are engine-specific. Each row (and the filter at the top) shows which. If you're unsure which engine you have, check the emissions label under the hood or the 8th character of your VIN.
What are the signs of belt drive problems on a 2021 Audi S4?
Common symptoms include squealing on cold start, a belt that shows cracking or glazing, or an accessory that slows under load. If you notice any of these, identify the affected subcategory above and cross-reference the part numbers listed.
What should I replace at the same time?
Where labor overlaps, replace the tensioner and idler pulleys with any belt at higher mileage — the labor overlaps almost entirely.
What do the market flags (US, CA, MX) on each part mean?
They show the market for which the manufacturer published application data for that part — where the vehicle was first sold, not where the part was made. If your 2021 Audi S4 was originally sold in the US, the safest choice is a part marked for the US market.
How do I make sure a part fits my 2021 Audi S4?
First match the engine — each row shows which engine(s) the part fits. Then a new belt on a worn tensioner will squeal within weeks — check tensioner damping and idler bearings while the belt is off. The notes column carries position and trim qualifiers where they apply.
Other Parts for the 2021 Audi S4
Belt Drive Parts for Other Audi S4 Years
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