TonGass 42" Lawn Mower Deck Belt Compatible with JohnDeere Lawn Mower Replaces Part Number GX20072 Flat Belts GY20570 Deck Drive Belt for Heavy-Duty Use Compatible with 100 D100 E100 Series

What It Is

The TonGass 42" deck belt is an aftermarket drive belt designed to transfer power from the engine pulley to the mower deck blades on select John Deere lawn tractors. It’s built for heavy-duty residential mowing and replaces OEM part numbers GX20072 and GY20570.

Fitment & Compatibility

Before buying, confirm your mower has a 42-inch stamped deck (not a 48" or 54"). This belt fits John Deere 100, D100, and E100 series tractors, including models like D105, D110, D125, D130, D140, D150, D155, D160, D170, E100, E110, E120, E130, E140, E150, E160, E170, and LA105, LA110, LA115, LA120, LA125, LA130, LA135, LA140, LA145, LA150, LA155, L100, L107, L108, L110, L111, L118, L120, L130. It will not fit X300, X500, or Z-series models. Measure your old belt’s length (should be 92.5" nominal) and width (1/2"). The TonGass belt is 1/2" x 92.5" – if yours is different, it won’t work. Verify your deck’s spindle and idler pulley arrangement matches the standard 42" 2-blade deck routing.

Key Things to Know

• Quality vs. OEM: This belt is slightly thinner and less durable than a genuine John Deere belt (GX20072 or GY20570). Expect 1-2 seasons of normal use; heavy or wet grass may shorten life.
• Installation: Moderate difficulty – requires releasing the idler pulley spring tension and routing around three spindles and two idlers. A diagram is usually printed under the deck or in your owner’s manual.
• Common gotcha: If your deck has a 4.5" or 5" engine pulley, the belt routing may differ. Check your specific model’s routing diagram online before installing.
• Noise: Some users report slight squeaking on initial use; this usually settles after a few minutes of running.

Should You Buy It

If you need a budget-friendly belt for light-to-moderate residential mowing and don’t mind replacing it annually, the TonGass is a solid choice. For heavy use, tall grass, or commercial work, spend more on an OEM belt – it will last longer and reduce downtime.