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Kubota B3150, B3200, B3350 - Transmission and PTO

Kubota B3150, B3200, B3350 Transmission - Hydraulic Circuit

Hydrostatic Transmission

1 - Bi-Speed Turn Clutch, 2 - Bi-Speed Turn Valve 2, 3 - Bi-Speed Turn Valve 1, 4 - Regulating Valve, 5 - Independent PTO Valve, 6 - Independent PTO Clutch, A - To 3-Points Hitch, B - HST

Manual Transmission

1 - Bi-Speed Turn Clutch, 2 - Bi-Speed Turn Valve 2, 3 - Bi-Speed Turn Valve 1, 4 - Regulating Valve, 5 - Power Steering Controller, A - To 3-Points Hitch, P - From Pump Port

Kubota B3150, B3200, B3350 Transmission - Oil Flow And Valves

1 - Oil Filter Cartridge (for HST), 2 - Swashplate, 3 - Cylinder Block (for Pump), 4 - Charge Relief Valve, 5 - Piston, 6 - Cylinder Block (for Motor), 7 - Check and High Pressure Relief Valve (for Forward), 8 - Check and High Pressure Relief Valve (for Reverse), 9 - Neutral Valve (for Forward), 10 - Neutral Valve (for Reverse), 11 - Independent PTO Control Valve, 12 - Oil Cooler, 13 - Power Steering, 14 - Hydraulic Pump (for Power Steering, Independent PTO, HST), 15 - Oil Tank, 16 - Hydraulic Pump (for 3-points Hitch), 17 - Hydraulic Control Valve (for 3-points Hitch), 18 - Oil Filter Cartridge

The pump and the motor are joined in a closed hydraulic circuit. Most of oil circulates with in the main oil circuit. A little oil lubricates and oozes out from the clearance between the moving parts in the case. Then oil in the main oil circuit of the HST needs to be supplied a want. So all of oil fed from hydraulic pump flow to hydraulic transmission for charging and cooling. The charge oil aids smooth operation of pistons for pump and motor. The charge oil passed to charge relief valve port. The rest of oil passed through the charge relief valve into the HST housing. And overflow oil from HST housing return to the transmission case.

Neutral

1 - Oil Filter Cartridge (for HST), 2 - Swashplate, 3 - Cylinder Block (for Pump), 4 - Charge Relief Valve, 5 - Piston, 6 - Cylinder Block (for Motor), 7 - Check and High Pressure Relief Valve (for Forward), 8 - Check and High Pressure Relief Valve (for Reverse), 9 - Neutral Valve (for Forward), 10 - Neutral Valve (for Reverse), 11 - Independent PTO Control Valve, 12 - Oil Cooler, 13 - Power Steering, 14 - Hydraulic Pump (for Power Steering, Independent PTO, HST), 15 - Oil Tank, 16 - Hydraulic Pump (for 3-points Hitch), 17 - Hydraulic Control Valve (for 3-points Hitch), 18 - Oil Filter Cartridge, A - Pump A Port, B - Pump B Port, C - Motor C Port, D - Motor D Port, a - High Pressure Oil, b - Low Pressure Oil, c - Free Oil, d - Suction Oil

When the speed control pedal (HST pedal) is in "Neutral", the variable swashplate is right-angles to the pump pistons. And the pump pistons only rotate with cylinder block (pump) without reciprocating. Since the oil is not being pumped to the motor, the cylinder block (motor) is stationary. And the output shaft does not rotate.

Forward

1 - Oil Filter Cartridge (for HST), 2 - Swashplate, 3 - Cylinder Block (for Pump), 4 - Charge Relief Valve, 5 - Piston, 6 - Cylinder Block (for Motor), 7 - Check and High Pressure Relief Valve (for Forward), 8 - Check and High Pressure Relief Valve (for Reverse), 9 - Neutral Valve (for Forward), 10 - Neutral Valve (for Reverse), 11 - Independent PTO Control Valve, 12 - Oil Cooler, 13 - Power Steering, 14 - Hydraulic Pump (for Power Steering, Independent PTO, HST), 15 - Oil Tank, 16 - Hydraulic Pump (for 3-points Hitch), 17 - Hydraulic Control Valve (for 3-points Hitch), 18 - Oil Filter Cartridge, A - Pump A Port, B - Pump B Port, C - Motor C Port, D - Motor D Port, a - High Pressure Oil, b - Low Pressure Oil, c - Free Oil, d - Suction Oil

When the speed control pedal (HST pedal) is stepped on and set to "Forward", the variable swashplate is tilted as shown in figure above. As the pump cylinder block rotates with the input shaft, oil is forced out of pump port A at high pressure. As pressure oil from the pump cylinder block enters to motor port C, the pistons, which align with port C, are pushed against the swashplate and slide down the inclined surface. Then the output shaft rotates with the motor cylinder block. This drives the machine forward and the angle of pump swashplate determines the output speed. As the motor cylinder block continues to rotate, oil is forced out of motor port D at low pressure and retunes to the pump port B.

Reverse

1 - Oil Filter Cartridge (for Hydrostatic Transmission), 2 - Swashplate, 3 - Cylinder Block (for Pump), 4 - Charge Relief Valve, 5 - Piston, 6 - Cylinder Block (for Motor), 7 - Check and High Pressure Relief Valve (for Forward), 8 - Check and High Pressure Relief Valve (for Reverse), 9 - Neutral Valve (for Forward), 10 - Neutral Valve (for Reverse), 11 - Independent PTO Control Valve, 12 - Oil Cooler, 13 - Power Steering, 14 - Hydraulic Pump (for Power Steering, Independent PTO, HST), 15 - Oil Tank, 16 - Hydraulic Pump (for 3-points Hitch), 17 - Hydraulic Control Valve (for 3-points Hitch), 18 - Oil Filter Cartridge, A - Pump A Port, B - Pump B Port, C - Motor C Port, D - Motor D Port, a - High Pressure Oil, b - Low Pressure Oil, c - Free Oil, d - Suction Oil

When the speed control pedal (HST pedal) is stepped on and set to "Reverse", the variable swashplate is tilted as shown in figure above. As the pump cylinder block rotates with the input shaft, oil is forced out of pump port B at high pressure. As pressure oil from the pump cylinder block enters to motor port D, the pistons, which align with port D, are pushed against the swashplate and slide down the inclined surface. Then the output shaft rotates with the motor cylinder block. This drives the machine reward and the angle of pump swashplate determines the output speed. As the motor cylinder block continues to rotate, oil is forced out of motor port C at low pressure and retunes to the pump port A.

Kubota B3150, B3200, B3350 Tractor - Transmission Linkage

Cruise Control Linkage (Tractors with Cab)

1 - Cruise Control Lever, 2 - Cruise Link Lever, 3 - Cruise Rear Rod, 4 - Cruise Front Rod, 5 - Neutral Holder, 6 - HST Plate, 7 - Trunnion Shaft, 8 - HST Lever, 9 - HST Pedal, 10 - Release Lever

Cruise control system mainly consists of cruise control lever holding section and cruise control releasing section. When the cruise control lever (1) is set to the desired position, the bottom end of the cruise link lever (2) turns clockwise. The control lever (1) pulls the cruise rear rod (3). The cruise rear rod (3) pulls the cruise front rod (4). The cruise front rod (4) pulls the neutral holder (5). The HST plate (6) is pulled by the cruise front rod (4). Since the neutral holder (5) turns clockwise, the trunnion shaft (7) directly attached to the neutral holder (5) turns clockwise. On the other hand, since the HST plate (6) pulls the HST lever (8) and the HST pedal (9). The HST pedal (9) is turned to the front side. On the other hand, since release lever (10) engage with tooth of lever guide RH, the cruise control lever (1) is held at the desired cruise position until the brake pedals will be depressed by an operator.

Cruise Control Release

1 - Brake Pedal, 2 - Cruise Cable, 3 - Cruise Control Lever, 4 - Return Spring, 5 - Return Spring, 6 - Neutral Holder, 7 - Trunnion Shaft, 8 - HST Plate, 9 - HST Pedal

Cruise control release is done by depressing the brake pedals (1). When an operator depresses the brake pedal (1), the cruise cable (2) is pulled by the brake pedals (1). At the time, the cruise control lever (3) is free. The cruise control lever (3) is returned to "NEUTRAL" position by the return spring (4). On the other hand, the return spring (5) pulls the neutral holder (6). The neutral holder (6) and the trunnion shaft (7) turns counterclockwise. Since the neutral holder (6) is connected to the HST plate (8), the HST plate (8) is pushed to the front side. The HST plate (8) pushes the HST pedal (9) to return to "NEUTRAL" position.

Cruise Control Linkage (ROPS Models)

1 - Cruise Control Lever, 2 - Cruise Lock 1, 3 - Release Wire, 4 - Roller, 5 - Neutral Holder, 6 - Trunnion Shaft, 7 - HST Pedal, 8 - Brake Pedal, 9 - Cruise Lock 2, 10 - Brake Rod, 11 - Cruise Rod, 12 - HST Plate, 13 - Hydrostatic Transmission Lever

When depressing the HST pedal (7) to "Forward", the HST lever (13), the cruise rod (11) and the cruise lock 2 (9) moves forward. And when the cruise control lever (1) is set to the desired position, the cruise lock 1 (2) is locked to the cruise lock 2 (9) and travelling speed is held to the desired speed.

When depressing the brake pedals, the release wire (3), the cruise control lever (1) and the cruise lock 1 (2) moves back. And the cruise lock 1 (2) release from the cruise lock 2 (9). Cruise lock is changed from "ON" to "OFF" position. Since the cruise lock is kept "OFF", the neutral holder turns counterclockwise, and the roller is returned to "Neutral" position. The HST pedal (7) also returns to "Neutral" position and the tractor stops.

Kubota B3150, B3200, B3350 Tractor - Independent PTO

Hydraulic Circuit

1 - PTO Clutch, 2 - Independent PTO Lever, 3 - Independent PTO Control Valve, 4 - Relief Valve, 5 - Oil Cooler, 6 - Oil Filter Cartridge (for HST), 7 - HST, 8 - Power Steering, 9 - Hydraulic Pump (for HST, Power Steering and Independent PTO), 10 - Oil Filter Cartridge, 11 - Hydraulic Pump (3-Points Hitch), 12 - 3-Points Hitch

Independent PTO Control Valve

1 - Transmission Case, 2 - Independent PTO Control Valve, 3 - PTO Arm, 4 - Control Rod, 5 - Poppet, 6 - Spring, 7 - Ball, 8 - Spring, A - PTO arm "OFF" position, B - PTO arm "ON" position

Independent PTO control valve (2) is located at transmission case (1). The independent PTO control valve (2) consists of PTO arm (3), poppet (5), ball (7) and etc. The PTO arm (3) is connected to control rod (4) and the independent PTO lever. The PTO arm (3) is moved to "OFF" or "ON" position by the independent PTO lever. Oil passage in the PTO arm (3) is turned by the independent PTO lever. When the PTO arm (3) is moved to "OFF" position, oil in the independent PTO control valve does not flow to the oil passage. When the PTO arm (3) is moved to "ON" position, oil in the independent PTO control valve flow to the oil passage. Poppet (5) and spring (6) operate as a relief valve.

Independent PTO Lever Engaged

When the independent PTO lever is shifted to the "ENGAGED" position, the PTO arm (3) is turned to "ON" position. Hydraulic oil from P port flows through oil passage (7) of the PTO arm (3), oil passage S1 in the transmission case (6) and oil passage S2 in the PTO clutch shaft (5) to the PTO clutch (4). Since the piston of the PTO clutch (4) is pushed by pressurized oil, clutch discs and clutch plates are pushed, and the PTO clutch (4) is engaged.

2 - Independent PTO Control Valve, 3 - PTO Arm, 4 - PTO Clutch, 5 - PTO Clutch Shaft, 6 - Transmission Case, 7 - Oil Passage (in the PTO Arm), P - Pump Port, H - HST Port, T - Tank Port, S1 - Oil Passage (in the Transmission Case), S2 - Oil Passage (in the PTO Clutch Shaft)

Independent PTO Lever Disengaged

When the independent PTO lever is shifted to the "DISENGAGED" position, the PTO arm (3) is turned to "OFF" position. Hydraulic oil is stopped at the PTO arm (3). This oil flows to the HST port. Oil in the PTO clutch (4) and the PTO clutch shaft (5) drains through oil passage S2, S1 and T port to the transmission case.

2 - Independent PTO Control Valve, 3 - PTO Arm, 4 - PTO Clutch, 5 - PTO Clutch Shaft, 6 - Transmission Case, P - Pump Port, H - HST Port, T - Tank Port, S1 - Oil Passage (in the Transmission Case), S2 - Oil Passage (in the PTO Clutch Shaft)

Kubota B3150, B3200, B3350 Transmission - Checking And Adjusting

Readjustment of Relief Valve (HST doesn't work due to its loose hex. socket head screw)

1 - Relief Valve Assembly, 2 - Hexagon Socket Head Screw, 3 - Relief Valve Assembling Tool, 4 - Poppet, 5 - Valve Seat

Measure the pre-adjustment distance "A". Compress the spring of the relief valve with a relief valve assembling tool (3). Then, find the distance "A" by turning the poppet (4) with a screwdriver. The distance "A" changes by about 0.5 mm (0.0197 in.) per one turn of the poppet (4). Repeat the same operation a few times to find the distance "A" as it is difficult to acquire at the first time. After finding the distance "A", hold the setscrew (6) to a vice and fasten the hexagon socket head screw (2) with specified torque. On this occasion, use a copper plate, etc. for the vice jaws not to damage the setscrew (6). Install the relief valve in the HST. Check the relief pressure. The distance "A" is for refresh only. Make sure to check the relief pressure after readjustment. The pressure changes by 1.47 MPa (213.3 psi) per 0.1 mm (0.0039 in.) in distance "A". Relief valve readjusting pressure - 31.4 to 35.3 MPa (4551 to 5120 psi). Distance "A" - 37.9 to 38.0 mm (1.4921 to 1.4960 in).

Kubota B3150, B3200, B3350 - Hydrostatic Transmission Service

Motor Shaft and Pump Shaft

Pull out the pump shaft from the HST housing case. Check the oil seal surface the bearing surface and the bearing. If the shaft is rough or grooved, replace it. If the bearing is worn, replace it. Motor Shaft - Pull out the motor shaft from the HST housing case. Check the oil seal surface the bearing surface and the bearing. If the shaft is rough or grooved, replace it. If the bearing is worn, replace it.

Cylinder Block Bore and Pistons

Lift all the pistons gently with the retainer plate. Check the pistons for their free movement in the cylinder block bores. If the piston or the cylinder block bore is scored, replace cylinder block assembly. Do not interchange pistons between pump and motor cylinder block. Pistons and cylinder blocks are matched. Piston Slipper and Retainer Plate - Check the slipper for flatness. If rounded, replace piston. Measure the thickness of piston slipper. If the measurement is less than the allowable limit, replace the piston. Check the lubricant hole for clogging. Thickness of slipper - 3.00 mm (0.118 in).

Cylinder Block Face and Trunnion Shaft Cover

Check the polished face of cylinder block for scoring. If scored, replace cylinder block assembly. Check the spring for breakage. If broken, replace cylinder block assembly. Trunnion Shaft Cover - Check the bearing for scratches and excessive wear. If worn or scored, replace it. Check the oil seal and the O-rings for damage.

Valve Plate and Center Section Face

Check the engagement of the valve plate and the anchor pin. Pushing the valve plate against the anchor pin, lift it to remove. Check the valve plate for foreign particles. Clean the valve plate and dry with compressed air. Check the valve plate for scratches, wear and erosion. If worn or scored, replace it.

Thrust Plates and Bearing Surface

Check the thrust plate for scratches and excessive wear. If worn or scored, replace it. Check the bearing surface of trunnion shaft (swashplate) for scratches and excessive wear. If worn or scored, replace it.

Center Section Oil Seals and Bearings

Check the oil seals for damage. Check the needle bearings for wear. If the needle bearings and oil seals are worn, replace all seals and needle bearings. After checking, coat the bearing with hydrostatic transmission oil and the oil seal lip with grease.

Check and High Pressure Relief Valve

Check the valve plug and valve for scratches and damage. Check the valve seat in the port block for damage. Check the spring for breakage and wear. If anything unusual, replace the check and high pressure relief valve assembly.

Neutral Valve and Charge Relief Valve

Check the holes of the valve body and the neutral valve for clogging. If clogged, open hole with compressed air. Replace the O-rings and the backup ring for scratches and damage. Check the springs for breakage and wear. If the valve surface is scored, replace it. If anything is unusual, replace it. Charge Relief Valve - Check the spring for breakage and wear. If it is unusual, replace it.

Cylinder Block Bore and Pistons

Lift all the pistons gently with the retainer plate. Check the pistons for their free movement in the cylinder block bores. If the piston or the cylinder block bore is scored, replace cylinder block assembly. Clearance between piston and bore - 0.02 mm (0.0008 in). Allowable limit - 0.04 mm (0.0016 in).

Kubota B3150, B3200, B3350 - Independent PTO Clutch Service

Bearing Check

Hold the inner race, and push and pull the outer race in all directions to check for wear and roughness. Apply transmission fluid to the bearing, and hold the inner race. Then, turn the outer race to check rotation. If there is any defect, replace it.

Clutch Disc Wear

Measure the clutch disc thickness with vernier calipers. If the thickness is less than the allowable limit, replace it. Clutch disc wear - 1.70 to 1.90 mm (0.067 to 0.075 in). Allowable limit - 1.55 mm (0.061 in).

Steel Plate and Pressure Plate Wear

Measure the steel plate thickness with vernier calipers. Measure the pressure plate thickness with vernier calipers. If the thickness is less than the allowable limit, replace. Steel plate wear (without hole) - 0.95 to 1.05 mm (0.0374 to 0.0413 in). Allowable limit - 0.8 mm (0.031 in). Steel plate wear (with holes, with holes and rubber plugs) - 1.15 to 1.25 mm (0.045 to 0.049 in). Allowable limit - 1.10 mm (0.043 in). Pressure plate wear - 1.95 to 2.05 mm (0.0768 to 0.0807 in). Allowable limit - 1.8 mm (0.071 in).

Piston Return Spring Free Length and Tension

Measure the free length of the piston return spring with vernier calipers. Place the piston return spring on a spring compression tester and compress to the specified length, and read the gauge. If the measurement is less than the allowable limit, replace. Piston / return spring free length - 34.5 mm (1.36 in). Piston return spring tension - 614.2 N / 17.8 mm.

KUBOTA TRACTORS TROUBLESHOOTING
L235	L2501	L2550	L275	L3110
L3301	L35	L3710	L3901	L4310
L5030	M4700	M5700	M6040	M6800
M8200	M8540	M9000	MX5100	MX5200