How to Fix a Leaking Transmission on a John Deer 325 Garden Tractor

Park the 325 on a flat, even surface and engage the parking brake.

Set the drip pan beneath the transmission drain plug and then remove the plug with the socket set. Before removing the plug, though, run your finger around the plug area to feel for excess fluid. If there is liquid on the outside of the plug, this is where the leak is occurring.

Allow the fluid to drain completely from the transmission into the drip pan. Run your fingers along the threads of the drain plug to feel for nicks or mis-threads. Wipe it down with a shop rag. Also wipe the drain plug hole on the underside of the transmission.

Spray some liquid thread seal, like Lock-Tite, onto the drain hole threads. Screw in a new replacement drain plug and tighten it with the socket set.

Inspect the access cap area for the internal filter located to the right of the drain plug. Feel for leaking fluid.

Use pliers to loosen and remove the internal filter access cap and then remove the spring and spacer. Slide the filter out and remove it and the old O-rings from the fluid line. Dry the area out well with a shop rag.

Set a new O-ring in place followed by the new filter. Spray the inside of the line connector with thread seal and then connect the new filter to it. Insert a new spring and spacer, which will come with the replacement filter kit along with the O-rings. Also replace the access cap firmly with the pliers.

Remove the transmission fluid dipstick, which is on the top side of the transmission on the left hand side of the mower. Insert a funnel and add Low Viscosity HY-GARD (J20D) transmission oil.

Park the mower in an area where you can monitor the transmission fluid and place some old newspaper beneath the transmission. If fluid continues to collect, have the mower serviced by a John Deere service repair shop.