Hydraulic Pump

Tractors may be equipped with either Sun-strand or Plessy hydraulic gear type pumps. The max­imum pump output is controlled by engine rpm and the number of teeth on the pump drive gear. The priority flow divider sends approximately 3 gpm to the steering system and the balance is used for the draft and position controls on the hitch lift system and for the auxiliary control valves.

Overhaul
To remove the hydraulic pump, first drain all compartments of Hy-Tran Plus fluid. Although the pump can be removed with left rear wheel Installed, most mechanics prefer to remove left rear wheel to provide more room to remove the multiple control valve and pump assembly.





Thoroughly clean the area around the multiple control valve, then remove the hydraulic filter assembly (15 through 20—Fig, 1). Disconnect steering lines, oil cooler line, hitch supply line, auxiliary valves return line and pto line from multiple control valve (13). Immediately cap or plug all openings. On models equipped with XL cab, remove left console. On all models, disconnect and remove park brake warning switch wires and linkage. Disconnect and remove pto operating lever. Remove two cap screws from oppo­site sides of multiple control valve. Install two 3/8 x 5 inch guide studs in the holes to aid in removal and installation of the assembly. Remove the balance of the retaining cap screws, then slide multiple control valve outward from rear main frame. Lay the assembly on a clean bench. Remove the four cap screws and copper washers, then lift off hydraulic pump assembly (2) and spacer plate (8), if so equipped.


Spacer plate (8) is used only on tractors equipped with a 23 tooth pump drive gear.
Disassembly of the pump is obvious after examination of the unit. Remove nut (5), drive gear (4) and Woodruff key (3). Remove end plate cap screws and separate pump components. Clean and inspect all parts. If any parts show excessive wear or other damage, renew pump assembly. A seal kit is available for resealing the pump. When reassembling pump, tighten end plate cap screws to a torque of 20-23 ft .-lbs. (27-31 N-m). Install Woodruff key (3), place drive gear (4) on shaft and install and tighten nut (5) to a torque of 45-50 ft.-lbs. (61-68 Nm). Hold drive gear in a vise while tightening nut. Check condition of foam seal (1). If damaged or loose, remove and discard seal. Clean seal area with a rag and adhesive solvent, then dry the housing. Apply a thin coat of oil resistant adhesive to the housing and to a new foam seal. Let adhesive dry one to two minutes, then install foam seal on pump housing. Allow adhesive to dry at least another 30 minutes before installing pump assembly.
When reassembling, use all new "O" rings, seal ring and gaskets. Install pump and spacer (8), if so equipped, to multiple control valve. Use new copper washers on the four pump retaining cap screws. Install and tighten cap screws to a torque of 18-24 ft.-lbs. (24-28 N-m).


Lubricate foam seal (1) with Hy-Tran Plus fluid and reinstall multiple control valve and pump assembly by reversing the removal procedure. Tighten multiple control valve retaining cap screws to a torque of 33-37 ft.-lbs. (45-50 N-m). Reinstall hand park brake linkage and pto linkage. Then, using a new filter ele­ment (15), "0" rings and gasket, install hydraulic filter assembly. Tighten filter center bolt to a torque of 12-16 ft.-lbs. (16-21 N-m). Connect all disconnected hydraulic lines. Fill transmission to correct level on dipstick with Hy-Tran Plus oil. Refill capacity is 36 U.S. quarts (34.0 L) on tractors without front drive axle and 38.6 U.S. quarts (36.5 L) on tractors with front drive axle.

Hydraulic pump test




To check flow and pressure of the hydraulic pump, first remove the plug (Fig. 2) for the flow divider. Remove spring (32) and spool (33), then reinstall plug. Remove the pilot relief valve (29) and install a test pilot relief valve. Disconnect the power steering supply pipe (directly below hydraulic filter). Cap the pipe and union on multiple control valve with high pressure caps. Disconnect hitch supply line (bottom rear line on multiple control valve) and cap the line. Connect the inlet hose from the flowmeter to the hitch supply union on the multiple control valve. Place outlet hose from flowmeter into transmission oil fill hole and wire in place. Fully open load valve on flowmeter. Start engine and operate at a speed of 2180 rpm. Record the flow. Close load control valve to obtain a reading of 2000 psi (13790 kPa) on pressure gage, then record the flow. Fully open the load valve and stop engine. The second flow reading must not be less than 90 percent of the first flow reading. If second reading is too low, check for the following conditions:
Low oil level.
Clogged filter.
Faulty pump.


Remove test pilot relief valve and using new seal rings, install original pilot relief valve. Remove flow divider plug (30) and install spool (33) and spring (32). Reinstall and tighten plug. Remove caps from steering supply line and union, then connect steering line. Disconnect and remove flowmeter and connect hitch supply line. Start tractor and bleed air from steering system