About : Two Hydraulic Filters
Many tractors with hydrostatic transmissions have two filters for the transmission. They are actually filtering the same oil and work in the same part of the tractor. A separate filter is used specifically for the hydrostatic drive because the system works in a loop sometimes circulating as little as a half gallon of fluid at a time. The second filter ensures that this small loop does not become contaminated since it does not regularly mix with the rest of the transmission fluids.
Kubota hydraulic filters New Holland hydraulic filters