Lawn Mower Hydrostatic Transmission Maintenance

Oil Viscosity and Quality

• John Deere's Product Manuals website recommends choosing oil viscosity based on air temperature range. In general it recommends SAE 20W-50 for air temperatures between 122 degrees Fahrenheit and -2 F -- which covers most situations -- but it stresses only high quality oil: no mixing with other oils, no "bio-oil" and no "Type F" (red) automatic transmission fluid. When checking oil levels, John Deere recommends it be 1 3/4 to 2 inches below the top of the oil tank filler neck.

Changing Oil and Filter

• The first step for changing the transmission oil and oil filter is letting the engine cool. Then comes removing the oil filter by turning it clockwise, possibly with the aid of an oil filter wrench, and taking it off the coupler. The inlet hose at the back of the coupler comes off and you can drain the transmission oil into a large container. Tractor maintenance writer Ronald Florence says having a big enough pan to collect the oil, and then facilities large enough to store it, are the hardest parts of the job. After replacing the plug and putting on a new filter, the only step is to fill the transmission oil tank to the recommended depth.

Pump Drive Belt

• The pump drive belt is self-adjusting, using a spring tensioner, but it must be checked regularly and replaced if necessary. A quick look under the driver's seat will show the belt on the transmission sheaves and the tensioner pulley. Replacing the belt, if worn, is made easier by carefully moving the spring loader idler with the help of a pry bar or large screwdriver.

Motion Control Linkages

• You can check the adjustment of the motion control linkages, which are part of the hydrostatic transmission system, when the machine is parked on a hard, level surface. After starting the engine, put the throttle at "1/2 fast." If the rear drive wheels begin to creep when you release the park brake, you will need an adjustment. The mower must go up on blocks or jack stands, and you must find the left and right motion control linkages, which connect pumps to the motion control assemblies, to make the adjustments.