Lawn Mower Tractor PTO Clutch John Deere, STX Series, Scotts Series *STX38 Lawn Tractor

The STX platform runs a 1-inch crankshaft bore - the correct fitment for the compact lawn tractor's smaller engine, and a distinct class from the 1-1/8-inch bore clutches on John Deere's larger garden tractors. A wrong-size clutch will not mount, or worse, risks crankshaft damage if forced. This clutch slides onto the STX's 1-inch crankshaft with the factory-specified fit - no adapters, no modification, no confusion between the STX and the larger 200/300-series clutch families.

Rated at 80 ft-lbs, this clutch is intentionally matched to the STX38's 12–13 HP engine and 38-inch deck - the engagement authority the machine needs, without the excess current draw of an over-specified clutch that would strain the compact platform's electrical system. The 80 ft-lb rating delivers reliable blade engagement through routine suburban mowing conditions - the exact duty cycle the STX38 was built for - while keeping the PTO switch and wiring within their design limits.

The STX38's "yellow vs green" legacy - John Deere green and Scotts-branded yellow variants of the same chassis - created parts confusion that persists today. This clutch covers both color schemes: the AM100979 path for the yellow/Scotts models and the AM119683 (Warner 5217-35) path for the STX38 and STX46. One clutch replaces both reference numbers, eliminating the risk of ordering the wrong variant for the wrong paint scheme and simplifying the parts counter decision for owners and shops alike.

The 5-3/8-inch pulley diameter is calibrated for the STX38's 38-inch and the STX46's 46-inch decks. At the engine's governed RPM, this pulley produces the exact blade-tip speed John Deere engineered for the compact STX deck - no belt-size changes, no deck-pulley swaps. Combined with the CCW rotation that matches the STX deck belt routing, the driveline geometry is factory-correct: consistent cut quality and predictable belt life across the machine's entire operating range.