AM134501 V-Idler Pulley AM138079 Compatible with John Deere X300 X304 X310 X320 X324 X330 X340 X350 X354 X370 X380 X384 X390 X394 X584 Replace AM138079 AUC11239 280-842

What It Is

The AM134501 V-Idler Pulley is a replacement belt guide pulley for select John Deere X300-series and X500-series lawn tractors, used to maintain belt tension and routing on the mower deck.

Fitment & Compatibility

Before buying, confirm your machine model and deck size. This pulley is compatible with John Deere X300, X304, X310, X320, X324, X330, X340, X350, X354, X370, X380, X384, X390, X394, and X584 tractors, typically with 42-, 48-, or 54-inch decks. It replaces OEM part AM138079, plus AUC11239 and 280-842. Measure the original pulley: this one is a 4-inch diameter, 5/8-inch bore, with a pressed metal construction. Verify your deck’s idler arm spacing and bolt size (usually 5/16-inch) before purchase. Aftermarket part; not OEM John Deere.

Key Things to Know

• Quality: At $11.58, it’s a budget option. Some users report shorter lifespan than OEM pulleys under heavy use or wet grass.
• Installation: Moderate difficulty. You’ll need a socket wrench and possibly a puller to remove the old pulley. Check belt routing diagram for your deck.
• Belt Compatibility: Works with most OEM and aftermarket belts, but ensure belt width matches the pulley groove (usually 1/2-inch).
• Common Gotcha: The pressed metal bearing can fail if the belt is overtightened or debris gets lodged. Inspect pulley spin before reinstalling belt.

Should You Buy It

Buy this if you need a low-cost replacement for a worn idler pulley on a John Deere X300-series mower and are comfortable with basic deck maintenance. It’s a decent value for light-to-moderate use, but if you mow frequently or in tough conditions, consider spending more on an OEM pulley for longer durability.