LAIKOU Mower Deck Gage Left Hand Rear Gauge Wheel Arm Compatible with John Deere AM138220 AM136329 for X300 X304 X320 X324 X340 X360 X500 X520 X530 X534 X540 X590 Series 48C & 54C Mower Decks

What It Is

This is a left-hand rear gauge wheel arm for John Deere X300–X590 series garden tractors equipped with 48C or 54C mower decks. It replaces OEM part AM138220 (and superseded AM136329) to support the deck’s rear corner, preventing scalping and uneven cuts on slopes or uneven terrain.

Fitment & Compatibility

• Exact fit: Left-hand rear only (right side uses a different arm).
• Compatible decks: 48C and 54C (48-inch and 54-inch stamped steel decks).
• Compatible tractors: X300, X304, X320, X324, X340, X360, X500, X520, X530, X534, X540, X590 series.
• Not compatible: X300R, X350R, X570, X580, X590 with 54” fabricated deck (uses different arm).
• Measure before buying: Overall arm length should be ~10.5” from pivot center to wheel axle center. Bolt hole spacing is 2.875” on center. Verify your existing arm matches these dimensions.
• OEM cross-reference: Replaces John Deere AM138220 (newer) and AM136329 (older). If your tractor originally used AM136329, this arm is a direct swap.

Key Things to Know

• Quality: LAIKOU is a budget aftermarket brand. Steel thickness and weld quality are adequate for residential use, but may not hold up as long as OEM under heavy commercial or rocky conditions.
• Installation: Simple bolt-on with two 3/8” bolts (not included). No drilling or modifications needed. Torque bolts to 30–35 ft-lb.
• Common gotcha: The wheel itself is often sold separately (check if your existing wheel fits the included axle stud). The arm does not include the wheel or hardware.
• Left vs. right: Double-check you’re buying the left-hand rear arm. The right-hand rear arm is a different part (AM138221/AM136328).

Should You Buy It

If you need a cheap, functional replacement for a worn or bent left rear gauge wheel arm on a residential John Deere X300–X590 with a 48C or 54C deck, this LAIKOU arm will work fine. For heavy commercial use or maximum durability, stick with OEM John Deere AM138220.