John Deere AUC17921 Pulley – Fits John Deere X300 Series Lawn Tractors (Replaces AM134501, AM138079)
John Deere AUC17921 Pulley – Fits John Deere X300 Series Lawn Tractors (Replaces AM134501, AM138079) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
John Deere AUC17921 Pulley – Fits John Deere X300 Series Lawn Tract...
Product Details
This John Deere AUC17921 Pulley is a high-quality V-idler pulley designed as a direct replacement for various John Deere X300 series lawn tractors. It ensures proper belt tension and smooth operation of your mower deck, fitting a wide range of models from the X300 to X584.
It serves as a direct interchange for multiple OEM part numbers, including John Deere AM134501, AM138079, AUC11239, AM134502, AUC11238, 280-842, and AM138080.
- Constructed from a high-strength composite for durability and longevity.
- Engineered for simple, direct replacement without specialized tools.
- Package includes two V-idler pulleys to complete your repair.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| John Deere | AM134501 |
| John Deere | AM138079 |
| John Deere | AUC11239 |
| John Deere | AM134502 |
| John Deere | AUC11238 |
| John Deere | 280-842 |
| John Deere | AM138080 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|
| John Deere | X300 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X300R | 4-Stroke | AM134501/AM138079 | |
| John Deere | X304 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X310 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X320 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X324 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X330 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X340 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X350 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X354 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X370 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X380 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X384 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X390 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X394 | 4-Stroke | AM134501/AM138079 | |
| John Deere | X584 | 4-Stroke | AM134501/AM138079 |
Technical Specs
- Product Type
- V-Idler Pulley
- Housing Material
- High Strength Composite
- Installation
- Direct replacement
- Product Dimensions
- 66.0 x 28.0 x 1.0
- Box Dimensions
- 66.0 x 28.0 x 1.0
What’s in the Box
- 2 x V Idler Pulley (AUC17921)
Installation Notes
Installation is straightforward and does not require specialized tools. Always consult your mower's service manual for detailed procedures and safety precautions.
- Ensure the mower engine is off and cool. Disconnect the spark plug wire for safety.
- Locate the idler pulley on the mower deck belt system. You may need to lower or remove the deck for access.
- Release the tension from the deck belt to loosen it around the pulleys.
- Using a suitable wrench, unbolt and remove the old idler pulley.
- Install the new AUC17921 idler pulley, ensuring it is correctly aligned and securely fastened.
- Reroute and re-tension the deck belt according to the manufacturer's specifications.
- Reconnect the spark plug wire, re-attach the mower deck if removed, and test the operation.
Troubleshooting & FAQ
How do I know if this pulley fits my John Deere tractor?
This pulley is designed for the John Deere X300, X300R, X304, X310, X320, X324, X330, X340, X350, X354, X370, X380, X384, X390, X394, and X584 models. Always verify by comparing your old part to our images and cross-referencing the part numbers in the 'Part Number Matrix' section against your machine's service manual.
What are the signs of a failing idler pulley?
Common symptoms include a loud squealing or grinding noise from the mower deck, visible wobble or physical damage to the pulley, or the deck belt frequently slipping off. A worn pulley can cause poor cutting quality and premature belt failure.
When should I replace my idler pulley?
Inspect idler pulleys when performing regular mower maintenance or whenever replacing the deck belt. They should be replaced if they feel rough or seize when spun by hand, show visible signs of cracking, or have excessive play.
Is this a set of two pulleys?
Yes, this listing includes two identical V-idler pulleys. Many mower decks use multiple pulleys of the same type, so this package allows for a complete replacement.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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