Losing Hydraulic Lift as Oil Temperature Increases

I am working on the lift system of the family TO-30. It loses lift as the gear oil increases in temperature. I have seen a piston on the internet with one ring, and that apparently uses an O-ring, and Teflon or leather backer. Would the O-ring piston reduce the loss of lift with increased temperature? What is the benefit of the O-ring piston? May 28, 2015.

The piston with an O-ring and backup ring is a Ford NAA part. This piston can be fitted to the Ferguson TE-20, TO-20 and TO-30 as a alternative to the original Ferguson piston with 3 rings. The Ford NAA piston will provide a better seal than the original Ferguson piston and will work well even if the original lift cylinder is scratched or has some surface imperfections.

From your description of the problem, you should also consider replacing the pump safety valve. Replacing the safety valve, piston and rings and changing the transmission/hydraulic oil generally improves the performance of these earlier Ferguson tractors. Make sure you use SAE 90 wt. Mineral Oil in the transmission/hydraulic system as it will provide the best overall performance. You can purchase this oil from Tractor Supply Company. See the attached link.

http://www.tractorsupply.com/en/store/travellerreg%3B-ford-tractor-all-mineral-90-transmission-fluid-2-gal