How to add fluid to husqvarna hydrostatic transmission

The hydrostatic transmission in your lawn tractor requires servicing that includes draining the old hydrostatic oil, changing the filter and adding new hydrostatic oil. Hydrostatic transmissions consist of a hydraulic pump and motor that is generally belt-driven from the lawn tractor engine to propel the lawn tractor forward and backward by a foot controlled pedal or hand lever. The hydrostatic transmission oil fill reservoir is generally located under the lawn tractor seat, but some model lawn tractors have two transmission oil fill reservoirs.

1. 1.

   Park the lawn tractor on a flat, level working surface and allow the engine an transmission to fully cool before filling the transmission. Set the lawn tractor park brake to prevent the lawn tractor from shifting or rolling while working.

2. 2.

   Slide an oil-catch drain pan directly under the hydrostatic transmission oil drain plug to catch the old transmission oil. The transmission oil drain plug is generally located on the side of the transmission towards the bottom. Some lawn tractor make and model hydrostatic transmissions may have one or more transmission oil drain plugs, one for the hydrostatic transmission side the other for the differential gear side.

3. 3.

   Clean dirt and debris from around the hydrostatic transmission oil reservoir cap with a clean shop towel to prevent the hydrostatic transmission and the transmission oiling system from contamination. Some hydrostatic transmissions have more than one transmission oil reservoir located under the lawn tractor seat: one that fills the hydrostatic transmission side and the other fills the differential gear side. Both the differential and hydrostatic transmission are connected by an internal cavity.

4. 4.

   Loosen the hydrostatic transmission oil reservoir cap by hand to allow the transmission oil to drain. A loose cap allows air to enter the oiling system, eliminating air vacuum and providing better oil flow drainage.

5. 5.

   Unscrew the hydrostatic transmission oil drain plugs with a socket wrench, and allow the transmission oil to fully drain.

6. 6.

   Screw the transmission oil drain plugs into the transmission. Torque the transmission oil drain plugs with a socket and torque wrench. Refer to your lawn tractor manufacturer's owner operator's manual for specific transmission oil drain plug torque specifications.

7. 7.

   Slide the transmission oil drain pan directly under the hydrostatic transmission oil filter. Some make and model hydrostatic transmissions are equipped with an transmission oil filter to clean the transmission oil, lengthening the transmission oil life.

8. 8.

   Unscrew the hydrostatic transmission oil filter from the transmission oil filter housing with an oil filter wrench. Slide the oil filter wrench onto the oil filter. Turn the oil filter counterclockwise to unscrew the transmission oil filter from the oil filter housing.

9. 9.

   Apply a light coat of clean hydrostatic transmission oil to the new transmission oil filter seal with your finger. Screw the new oil filter onto the oil filter housing by hand. Finish tightening the transmission oil filter with the oil filter wrench. Slide the transmission oil drain pan from under the transmission oil filter.

10. 10.

    Fill the hydrostatic transmission oil filter reservoirs with new hydrostatic transmission oil. Pour the transmission oil into the reservoirs by hand. Fill the oil reservoir to the full line that is embossed on the side of the reservoir tank.

11. 11.

    Screw the transmission oil reservoir fill caps onto the reservoir, and tighten the caps by hand. Start the lawn tractor engine. Check for transmission oil leaks around the transmission oil drain plugs and transmission filter housing. Drive the tractor in forward and reverse several times to check for proper transmission operation.

12. 12.

    Park the lawn tractor an a flat, level surface. Stop the lawn tractor engine and check the hydrostatic transmission oil level. Add additional transmission oil if necessary, bringing the oil level up to the full line on the transmission oil reservoir.

    Things You Will Need

    • Oil catch drain pan

    • Clean shop towel

    • Socket wrench

    • Socket

    • Torque wrench

    • Oil filter wrench

    • Hydrostatic transmission oil

    • Hydrostatic transmission oil filter

    Tip

    Always check the hydrostatic transmission oil level when the engine and transmission are cool. Hydrostatic transmission oil expands with heat and can give a false reading when hot.

Hydrostatic transmissions use oil, under pressure, to provide movement for the tractor. The fluid is pressurized with a pump inside the transmission. If any air is in the fluid, the pump will try to pressurize air. This condition is known as cavitation, and is detrimental to the pump since it allows the pump top operate dry. When the pump cavitates it is not pressurizing any fluid, so the transmission is not able to provide the movement needed.

If your mower is new, or has been stored for a long period (longer than 2 months) the transmission needs to be purged before use. Also, if you experience loss of drive, or slower response, then the transmission should be purged first.

 The following procedure will remove trapped air inside the transmission(s).

IMPORTANT: SHOULD YOUR TRANSMISSION REQUIRE REMOVAL FOR SERVICE OR REPLACEMENT, IT SHOULD BE PURGED AFTER REINSTALLATION BEFORE OPERATING THE TRACTOR.

Step 1- Place the rear of the mower safely onto jackstands on a level surface with engine off and parking brake set.

Step 2- Disengage transmission by placing freewheel control, located at the back of the frame, in the freewheeling position.

          2a- Mowers with seperate pumps and wheel motors the freewheel is activated by turnign the bypass valves, one on each pump, two full turns.
          The oil resevoir needs to be filled to the specifications listed in the owners manual before starting the purge procedure.

Step 3- Sitting in the operators seat(riders), start engine. After the engine is running, move throttle control to slow position. With motion control levers in neutral (N) position, slowly disengage clutch/brake pedal.

Step 4-Move motion control levers to full forward position and hold for five (5) seconds. Move levers to full reverse position and hold for five (5) seconds. Repeat this procedure three (3) times.

NOTE: During this procedure there may be some movement of the drive wheels, but they are not under load. The air is being removed from hydraulic drive system.

Step 5-Move motion control levers to neutral (N) position. Shutoff engine and set parking brake. Check and add oil as needed for units with an oil resevoir.

Step 6-Engage transmission by placing freewheel control into driving position, or by closing the bypass valves on the pumps.

Step 7-Sitting in the operators seat, start engine. After the engine is running, move throttle control to full speed. With motion control levers in neutral (N) position, slowly disengage clutch/brake pedal.

Step 8-Slowly move motion control levers forward, after the tractor moves approximately five (5) feet, slowly move motion control levers to reverse position.
After the mower moves approximately five (5) feet return the motion control levers to the neutral (N) position. Repeat this procedure with the motion control levers three (3) times.

Step 9-Your mower is now purged and now ready for normal operation.

For further information or assistance, we recommend contacting your local authorized service center,

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