How to Fill a Hydrostatic Transmission in a Lawn Tractor

Lawn tractors with hydrostatic transmissions are very maneuverable due to their drive train system. The engine speeds up when gas is applied to the lawn tractor; the action drives a hydraulic pump at a higher speed to supply pressurized transmission fluid to the wheels and drive the wheels at a faster rate. A hand lever or foot pedals control the speed on this type of lawn tractor. Older models may need the addition of transmission fluid because of leaks in the reservoir tanks or hydraulic lines.

Step 1

Turn the lawn tractor off and park it on level ground. Let the engine cool completely.

Step 2

Tip the lawn tractor seat forward. Insert a screwdriver into each screw that holds the seat to the seat bracket. Turn each screw counterclockwise to loosen and remove it. Slide the seat off the seat bracket; the frame cover is underneath.

Step 3

Remove the screws holding the frame cover to the transmission case. Pull the cover straight up and off.

Step 4

Wipe the transmission oil tank off with a towel to see the lines on the tank.

Step 5

Grasp and unscrew the cap on the expansion tank next to the transmission tank in a counterclockwise direction.

Step 6

Place a small funnel in the filler tube of the tank and pour transmission fluid into the funnel. Observe the level on the tank and fill it to the "Oil level cold" mark on the tank.

Step 7

Remove the funnel and screw the oil filler cap on the reservoir in a clockwise direction.

Step 8

Align the frame cover screw holes on the lawn tractor frame. Replace each screw and tighten them clockwise.

Step 9

Slide the seat onto the seat bracket, replace the screws, and tighten them clockwise.