Hydraulic system overview
Hydraulic diagram

Hydraulic diagram

8R Series Tractor hydraulic system
Hydraulic oil filter

Hydraulic oil filter

Closed-center pressure and flow-compensated hydraulic system with load sensing reduces unnecessary engine load and improves fuel efficiency by providing pressure and flow only on demand.

By maintaining on demand pressure and flow, internal leakage is reduced, and the system generates less heat. Also, less strain is put on hoses and seals, providing a more reliable system. The use of flat-face O-rings provide leak-free connections.

The integration of the pumps, filter housing, and priority valve result in fewer and shorter lines, providing added reliability for greater productivity, less pressure loss and less flow restrictions.

The integrated pump assembly is attached to the right side of the pump drive housing. The charge pump section is a constant-flow gear-type pump. It draws oil through a suction screen from the rear differential case, providing low-pressure oil to the dual filtering system and to the integrated axial piston pump. Filtered oil not required by the axial piston pump is routed to the clean oil reservoir for transmission and ground drive pump usage.

An integrated axial piston pump is available in two sizes, 63-cc and 85-cc displacement. They are pressure-flow-compensated axial piston pumps and provide oil to steering, brakes, hitch, SCVs, as well as ILS™, ActiveSeat™, and to power-beyond functions if equipped.

The axial piston pump receives filtered oil from the low-pressure charge pump and provides system pressure from 4000 kPa (580 psi) to 19,995 kPa (2900 psi) upon demand.

All return oil is routed through the integrated dual filtering system, making clean oil available to the integrated axial piston pump. Oil not required by the axial piston pump is routed back to the clean-oil reservoir. 


The clean-oil reservoir is located in the top portion of the pump drive housing and holds 36 L (9.5 gal.) of filtered oil. It receives the excess oil not needed by the axial piston pump. It serves as a reservoir for filtered oil to be used by the transmission pumps. When needed, it also supplies filtered oil to the axial piston pump. With the use of large, single-acting cylinders, the axial piston pump may draw oil from the clean-oil reservoir. Reservoir overflow oil also provides necessary lubrication for spiral gear set in differential.

The hydraulic system is protected by an oil level switch located in the clean-oil reservoir. If oil level is low, secondary functions (SCV, hitch, power beyond) will be reduced, maintaining oil for steering and brakes. At the same time, an indicator light and code will be generated, notifying the operator of a low-oil situation. Once the low oil condition is resolved, secondary functions will be restored and the indicator will stop.

A temperature sensor located in the clean-oil reservoir protects the AutoPowr™/IVT™ and Automatic Powershift (PST) transmissions. Engine rpm will be reduced to 1500 rpm and only certain transmission speeds will be obtained with cold oil. Once oil temperature reaches an acceptable level, complete engine and transmission functions will be available.


Engine is reduced to 1500 rpm at oil temperature of -5° C or 23° F.
Ground speed is reduced to 4.8 km/h (3 mph) at an oil temperature of -5° C or 4° F.
Engine is reduced to 1500 rpm at oil temperature of -18° C or 0° F.

Transmission is reduced to a maximum of 14th gear at oil temperature of 3° C or 37° F.

A priority valve is also integrated with the hydraulic pumps and the filter housing, resulting in fewer and shorter lines providing added reliability. It ensures sufficient oil supply is available for steering and brakes at all times. Excess oil is then available for other hydraulic system functions such as SCVs, hitch, power beyond, ILS™, and ActiveSeat™.

The priority valve routes filtered oil directly from the axial piston pump, eliminating lines and resulting in less pressure loss and less flow restrictions.

Two 5 micron filters working in parallel filtering hydraulic and transmission oil results in 17 percent more flow capacity and extends filter service interval to 1500 hours.

The hydraulic filter housing contains a filter restriction switch with a bypass valve to ensure there is always oil available to hydraulic functions.

Each filter base has an anti-drain back check valve to prevent excessive oil drainage when servicing filters.

AutoPowr/IVT and PST transmission pumps are constant-flow gear-type pumps located on the left side of the pump drive housing. The inside pump section of the tandem pump on AutoPowr/IVT supplies the transmission’s hydro unit. The outside pump section on AutoPowr/IVT and the single pump on the PSTs perform the same functions. Not only do they provide oil for transmission functions, but they also supply PTO and differential lock control oil.

Base Equipment On : 8R and 8RT Series
Last Updated : 25-Jul-2013