Yard Machines, which are made by the MTD Company, have a line of mowers that utilize hydrostatic transmission. The advantage is that hydraulic pressure is used to shift gears, making it easier to mow on irregular terrain because the fluid is constantly adjusting. However, hydrostatic transmission, like other systems, can still have its problems.
Hydrostatic transmission systems in Yard Machines are connected to the engine and mower deck with belts. V belts link the hydraulic pumps to the engine, while a deck belt connects the transmission to the engine. These belts are tightly riding on pulleys and move once the engine is started. Pulleys damaged from rust or wear can cause tears or additional wear onto the belts. This can halt the hydrostatic transmission. If you change these belts, ensure you keep grease and oil off to prevent slippage.
A linkage adjustment may be needed if the mower tries to move while in the “neutral” position. Make adjustments by first putting your hydrostatic transmission in the neutral control position. Depress the clutch-brake pedal until the scissor brackets are together and then shut off the engine. After tightening the hex nut on the scissor mounting bracket, thread the speed selector rod out until the control lever is lined up with the neutral marking on the speed control index bracket. Tighten the jam nut on the ferrule, put everything back together, then test.
Hydrostatic transmission systems need a way to stay cool. Yard Machines use bypass engine oil, a fan and air fins to do this. Any compromise to those systems can result in an overheated condition, which will prevent gear shifting. Periodically inspect the air fins and fan for damage. Ensure your oil levels are full prior to operation. Change the oil according to the maintenance schedule as listed in the operator’s manual. This keeps sediments and sludge from building up in the engine, which can increase friction and raise engine temperatures.
Your ability to service the hydrostatic transmission system is limited, which may make it more expensive to fix. The hydrostatic transmission is a closed system. All hydraulic fluid is added at the factory before the system is sealed. If the level reader indicates a low fluid level or if there is a leak, you will have to take your Yard Machine to an authorized dealer for repair.