Flat Idler Pulley for AM146880 John Deere LT166 LT180 X300 X310 X350 X500 X580 S1642 S1742 Fits 42" 46" 48" Deck Lawn Mowers (2 Pack)

What It Is

This is a flat idler pulley (2-pack) designed for John Deere lawn tractors and zero-turn mowers, used to tension and guide the drive belt on 42", 46", and 48" cutting decks. It replaces OEM part AM146880 and is common on models like LT166, LT180, X300, X310, X350, X500, X580, S1642, and S1742.

Fitment & Compatibility

Before buying, verify three things:

• Deck size: Works only with 42", 46", or 48" decks – not for 54" or 60" decks.
• Model year: Compatible with most John Deere LT, X300, X500, and S-Series tractors built after 2000, but double-check your specific model’s parts diagram.
• Measurements: OEM AM146880 is 4" outer diameter, 3/8" wide groove, 5/8" bore. Measure your old pulley to confirm these dimensions – aftermarket tolerances can vary slightly.
• Belt type: Works with standard V-belts on these decks, not for Kevlar or metric belts.

Key Things to Know

• Quality: Aftermarket steel pulley with sealed bearing – good value, but bearing life may be shorter than OEM (expect 2-3 seasons vs 4-5 with genuine Deere).
• Installation: Simple bolt-on swap using a socket or wrench; no special tools needed. Torque to 20-25 ft-lbs – overtightening can warp the pulley.
• Gotcha: The included bolts may not match your deck’s thread pitch (often 5/16-18). Reuse your original hardware if needed.
• Pack size: 2-pack is handy for replacing both idlers at once, saving future downtime.

Should You Buy It

If you’re maintaining a John Deere with a 42-48” deck and want a budget-friendly replacement that works out of the box, this is a solid pick. It’s ideal for DIY owners who don’t need OEM longevity and prefer to keep two spares on hand. Skip it if you’re running a heavy-use commercial mower or need exact OEM fitment without measurement checks.