GX20072 Deck Drive Belt 42 inch Lawn Mower Deck Belt Compatible with John Deere GY20570 LA125 LA135 L100 L105 D100 D110 D120 D130 LA100 LA105 LA110 LA120.

What It Is

The GX20072 is an aftermarket 42-inch deck drive belt that transfers power from the engine pulley to the mower blades on select John Deere lawn tractors. It’s designed to replace OEM belts in residential mowing applications.

Fitment & Compatibility

Before buying, confirm your mower has a 42-inch stamped deck (not fabricated). This belt fits John Deere models: LA125, LA135, L100, L105, D100, D110, D120, D130, LA100, LA105, LA110, LA120, plus the LA series with suffix letters. It directly replaces OEM part numbers GY20570 and GX20072. Measure your old belt length (end-to-end, not circumference) – this belt is approximately 92.5 inches long and 1/2 inch wide. If your deck uses a different belt length or width (e.g., 1/2” x 93.5”), it won’t fit. Always cross-check with your mower’s manual or existing belt part number.

Key Things to Buy

• Quality vs OEM: This aftermarket belt is priced well below John Deere OEM ($25–$35). It’s made from standard rubber/polyester, not Kevlar-reinforced. Expect shorter lifespan (1–2 seasons vs 3–4 for OEM) in heavy or wet grass.
• Installation: Moderate difficulty. You’ll need to release the deck tensioner (spring-loaded), route the belt around pulleys, and re-tension. No special tools required, but a socket set and pliers help.
• Common gotchas: The belt may be slightly tighter or looser than OEM – check tension after first 15 minutes of use. If it squeals or slips, adjust the tensioner. Also verify your deck spindle pulleys spin freely; seized pulleys will shred any belt quickly.
• Measurement check: Measure your old belt flat (not looped). If it’s 92.5” long and 1/2” wide, this is correct. Any deviation means wrong part.

Should You Buy It

Buy this if you have a compatible 42-inch John Deere lawn tractor and want an affordable drop-in replacement for light residential mowing (weekly cuts, dry grass). Skip it if you mow tough conditions (thick, wet grass, rough terrain) or want maximum belt life – invest in OEM or a premium aftermarket brand like Oregon or Stens.