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Kubota B6200, B7200 - Hydrostatic Transmission

Kubota B6200HST, B7200HST Tractor - Transmission System

A - Hydrostatic transmission, B - PTO shift section (1-2-N), C - High-low gear shift section, D - One-way clutch cam section, E - Front wheel drive section (Engaged - Disengaged)

The transmission consists of HST (Hydrostatic Transmission) and a series of gears shown in pic. It offers the most suitable speeds for traveling and operation by combination of them. And power is transmitted to the front or rear axles and the PTO shafts, which are classified respectively as the traveling system and PTO system. The traveling system consists of the HST (A), high-low gear shift section (C) and front wheel drive section (E). The traveling speeds are selected by the operation of the speed control pedal and the high-low gear shift lever.

1 - Charge Relief Valve, 2 - Neutral Valve, 3 - Trunnion Shaft W Port Block, 5 - High Pressure Relief Valve, 6 - Variable Displacement Piston Pump, 7 - Charge Pump, 8 - Input Shaft, 9 - Case, 10 - Fixed Displacement Piston Motor, 11 - Output Shaft

1-Oil Filter Cartridge, 2-Joint, 3-Thrust Plate, 4-P3 Port, 5-Trocoid Rotor Assembly, 6-Charge Pump Case, 7-Input Shaft, 8-Oil Seal, 9-Ball Bearing, 10-Case, 11-Ball Bearing, 12-Fixed Swashplate, 13-Piston, 14-Cylinder Block, 15-Drain Plug, 16-Valve Plate, 17-Variable Swashplate, 18-Piston, 19-Cylinder Block, 20-Port Block, 21-Valve Plate, 22-Variable Displacement Piston Pump, 23-Oil Seal, 24-Case Relief Valve, 25-Fixed Displacement Piston Motor, 26-Oil Seal, 27-Output Shaft

1-Check Valve, 2-Neutral Valve (Forward), 3-Pump Kidney Port A, 4-Motor Kidney Port C, 5-Output Shaft, 6-P1 Port, 7-P2 Port, 8-Check Valve, 9-Charge Relief Valve, 10-Neutral Valve (Reverse), 11-Pump Kidney Port В, 12-Input Shaft, 13-Case Relief Valve, 14-Motor Kidney Port D, 15-High Pressure Relief Valve

Variable Swashplate

This pump is variable displacement one. The angle of its swashplate can be varied so that the volume and pressure of oil pumped by the pistons can be changed or the direction of oil flow can be reversed. The swashplate is moved around the trunnion shaft with the neutral holder, by stepping on the speed control pedal linked to the neutral holder.

Kubota B6200, B7200 Transmission - Oil Flow and Valves

P1. Port for checking high pressure (forward), P2. Port for checking high pressure (reverse), P3. Port for checking case pressure, P4. Port for checking vacuum, P5. Port for checking case pressure

The pump and motor are joined in a closed hydraulic loop and most of oil circulates within the main oil circuit. A little oil lubricates and oozes out from the clearance between the moving parts to the case. Then oil in the main oil circuit of the hydrostatic transmission needs to be supplied a want. So all of oil fed from the main hydraulic pump flows to the hydrostatic transmission for charging. Only return oil from the hydraulic cylinder drops to the transmission case. The charge oil aids smooth operation of piston pump and motor. The rest of the oil passes through the charge relief valve into the case. Then the oil passes to the main hydraulic pump through a cooler.

Neutral Valve

The neutral valves in the main oil circuit lines are open and pass the oil to the case when in neutral, and the oil pressure in their lines becomes low. And when the oil pressure in the high pressure line increases to a specified pressure, the neutral valve closes. Valve operating pressure - 3.24 MPa (469 psi).

High Pressure Relief Valve

The high pressure relief valve between the two lines in the main oil circuit monitors the oil pressure in each line. When excessively high pressure is built up in one line, it opens and flows the oil into another line. Valve operating pressure - 22.5 to 24.5 MPa (3270 to 3560 psi).

Case Relief Valve

The case relief valve monitors the oil pressure in the hydrostatic transmission case. When the oil pressure rises, it opens and flows the oil directly to the transmission case, so that the oil may not leak against the sealings. Valve operating pressure - 170 to 230 kPa (24 to 32 psi).

Kubota B6200, B7200 Transmission - Control Linkage

1-Neutral Holder, 2-Speed Control Rod, 3-Rod Guide, 4-Speed Set Device, 5-Damper, 6-Speed Control Pedal, 7-Neutral Holder Arm, 8-Roller

The speed control pedal (6) and the trunnion shaft of variable swashplate are linked with the rod guide (3), the speed control rod (2) and the neutral holder (1). As the front footrest of the pedal is depressed, the swashplate rotates and forward traveling speed increases. Depressing the rear footrest increases reverse speed. The roller (8) on the neutral holder arm (7) hanged with spring seats the detent of the neutral holder (1) so that the neutral holder returns to neutral. Then, the swashplate is returned to neutral with the neutral holder, when the pedal is released. The damper (5) connected to the rod guide (3) restricts the movement of the linkage to prevent abrupt operation or reversing. The speed set device (4) linked to the rod guide (3) enables the linkage not to return to neutral and to keep a certain forward speed while the speed control pedal (6) is released. On B6200, this device is installed as optional.

Kubota B6200HST, B7200HST Tractor - Mechanical Transmission

High-Low Gear Shift Section

Mechanical transmission receives engine power from the output shaft of hydrostatic transmission and selects high or low gear, and transmits the power to differential.

Neutral

1 - 14T Gear, 2 - 2nd Shaft, 3 - 24T Gear, 4 - 15T Gear, 5 - 23T Gear, 6 - 4th Shaft, 7 - 16T Gear, 8 - Output Shaft, 9 - 20T-12T Gear, 10 - Spiral Bevel Pinion

High or low speed is obtained by shifting 20T-12T gear (9) splined to spiral bevel pinion (10). When in neutral, neither 15T gear (4) nor 23T gear (5) meshes with 20T-12T gear (9) on spiral bevel pinion (10). Engine power is transmitted to the output shaft (8) of hydrostatic transmission, to which 16T gear (7) is splined. 16T gear (7) and 14T gear (1) are in mesh. 14T gear (1) is splined to 2nd shaft (2). Integral 11T gear on 2nd shaft (2) and 24T gear (3) are in mesh. 24T gear (3) is splined to 4th shaft (6). To 4th shaft (6), 15T gear (4) and 23T gear (5) are also splined. Spiral bevel pinion (10) is not driven.

Low

1 - 15T Gear, 2 - 20T-12T Gear, 3 - Spiral Bevel Pinion

20T-12T gear (2) is shifted and 20T gear meshes with 15T gear (1) splined to spiral bevel pinion (3). Then power is transmitted to differential.

High

1 - 23T Gear, 2 - 20T-12T Gear, 3 - Spiral Bevel Pinion

20T-12T gear (2) is shifted and 12T gear meshes with 23T gear (1) splined to spiral bevel pinion (3). Then power is transmitted to differential.

Front Wheel Drive Section (4WD-Type)

1 - Drive Shaft, 2 - Universal Joint, 3 - Front Wheel Drive Shaft, 4 - 24T Gear, 5 - 16T Gear, 6 - Spiral Bevel Pinion

The front wheel drive is used when greater traction power is required or to prevent the tractor from being pushed during rotary tilling of hard soil. 2-wheel drive or 4-wheel drive is selected by changing position of 24T gear (4) on the front wheel drive shaft (3) with the front drive lever. When the front drive lever is set to "Disengaged", 24T gear is in neutral and power is not transmitted to the front drive shaft. When the front drive lever is set to "Engaged", 24T gear slides rearward to engage with 16T gear (5) on the spiral bevel pinion shaft (6). Therefore, the front drive shaft is actuated to drive the front wheels.

Kubota B6200, B7200 - PTO Shift Section

PTO system is independent of HST. Engine revolution is directly transmitted to the 2nd shaft (4).

1 - Input Shaft of HST, 2 - 14T Gear, 3 - 18T Gear, 4 - 2nd Shaft, 5 - 21T Gear, 6 - Mid PTO Shaft, 7 - 21T Gear, 8 - 3rd Shaft, 9 - 17T Gear, 10 - Rear PTO Shaft

Neutral - The 14T gear (2) meshes with the 21T gear (5) on the 3rd shaft (8). And the 18T gear (3) meshes with the 17T gear (9) on the 3rd shaft (8), too. But the 21T gear (5) and the 17T gear (9) unite with needle bearing in itself, they run idle on the 3rd shaft (8). Then the 3rd shaft (8) is not driven.

1st Position - The 21T gear (7) splined to the 3rd shaft (8) is shifted forward, and then the 3rd shaft (8) is rotated. Rear PTO shaft (10) speed is 540 rpm at an engine speed of 2517 rpm. Mid PTO shaft (6) speed is 1546 rpm at an engine speed of 2517 rpm.

2nd Position - The 21T gear (7) shifted to the 3rd shaft (8) is shifted rearward, and then the 3rd shaft (8) is rotated. Rear PTO shaft (10) speed is 858 rpm at an engine speed of 2517 rpm. Mid PTO shaft (6) speed is 2456 rpm at an engine speed of 2517 rpm.

Kubota B6200, B7200 One-Way Clutch Cam Section

1 - 3rd Shaft, 2 - Clutch Cam, 3 - Clutch Cam, 4 - Cam Spring, 5 - 5th Shaft

The one-way clutch cam is also called an overrunning clutch. It is composed of a pair of clutch cams (2), (3) and a cam spring (4). One of the clutch cams is splined to the 3rd shaft (1), and the other is splined to the 5th shaft (5). These two clutch cams are engaged with each other by the force of the cam spring. As long as the 3rd shaft is rotating faster than the 5th shaft, these two clutch cams will remain engaged, and the 5th shaft is driven.

Kubota B6200, B7200 - Transmission Service

Transmission Oil Change

Remove the drain plugs to drain transmission oil. Screw in the drain plugs. Fill new oil up to the upper line on the dipstick

Transmission Oil Filter Cartridge Replacement

The oil filter cartridge must be replaced after initial 50 hours and every 200 service hours. Remove the bolts which secure the cover. Remove the oil filter cartridge by using the filter wrench. Lightly tighten the screw by using a screwdriver. Apply a slight coat of oil onto the cartridge gasket. To install the new cartridge, screw it in by hand. Over tightening may cause deformation of rubber gasket. After the new cartridge has been replaced, the transmission oil level will become a little lower. Make sure that the transmission oil does not leak through the seal. Check the oil level.

Kubota B6200, B7200 Hydrostatic Transmission (HST)

Remove the propeller shaft from the 1st shaft. Remove the drive shaft from the front wheel drive shaft (4WD type only). Remove the HST mounting screws, and remove the HST. After inserting the spring pin to the 1st shaft and drive shaft, lock the spring pin with a wire. HST mounting screw (Tightening torque) - 48 to 56 Nm (35.4 to 41.2 ft-lbs).

Control Valve and Top Link Bracket

Remove the control valve with the feedback rod (4WD type). Remove the control valve with the check rod (2WD type). Remove the top link bracket. Use care not to damage the О-rings on the control valve. Control valve mounting screw (B6200HST, B7200HST 4WD type) - 16.7 to 21.6 Nm (12.3 to 15.9 ft-lbs). Control valve mounting screw (B6200HST, B7200HST 2WD type) - 16.7 to 21.6 Nm (12.3 to 15.9 ft-lbs). Top link bracket mounting screw - 39.2 to 64.7 Nm (28.9 to 47.7 ft-lbs).

Separating Transmission Case

Remove the bolt. Remove the fork shaft lock screw. Remove the transmission case mounting nuts, and separate the transmission case. Apply liquid gasket (Three Bond 1102 or equivalent) to both sides of new gasket. Transmission case mounting nut (Tightening torque) - 39.2 to 64.7 N-m (28.9 to 47.7 ft-lbs).

Case and Case Relief Pressure Checking

Remove the 1/4 plug from port, with care not to allow any particle of sealing tape enter into the port. Install the long connector to port with sealing tape on its thread. Install the threaded joint to long connector with the gasket between them. Install the cable, threaded joint in relief valve set pressure tester and low pressure gauge to threaded joint in order. Run the engine at 2600 to 2700 rpm. Place the high-low shift lever in neutral. Release the speed control pedal to set in neutral. After measuring the case pressure, remove the eye joint from port and plug the port with 3/8 screw to measure the case relief pressure.

Kubota B6200HST, B7200HST - Mid-PTO

1 - 24T Gear, 2 - Screw, 3 - Shaft, 4 - 11T Gear Shaft, 5 - Cover, 6 - Oil Seal

Separate the mid-PTO case from the transmission case. Remove the mid-PTO case cover (5). Remove the screw (2) and pull out the mid-PTO counter shaft (3) and remove the 24T gear (1). Draw out the 11T gear shaft (4) with the bearing on it. After tapping the spring pin (2) into the shaft (3), remove the shaft (3) and the 24T gear (1). Remove the oil seal (6) and the external snap ring (5). Draw out the 11T gear shaft (4) with the bearing on it. Mid-PTO case cover to case - 14 to 20 Nm (10 to 14 ft-lbs). Mid-PTO case to transmission case - 48 to 56 Nm (35 to 41 ft-lbs).

PTO Shaft

1. Rear Cover, 2. 18T Gear, 3. Taper Roller Bearing, 4. Washer, 5. Lock Washer, 6. Screw, 7. PTO Shaft, 8. Bushing, 9. PTO Collar, 10. PTO Shim, 11. Taper Roller Bearing, 12. PTO Collar

Flatten the lock washer (5). Remove the screw (6), plain washer, lock washer (5), washer and straight pin. Tap out the PTO shaft (7) to the rear. Replace the lock washer with a new one, and be sure to adjust the turning torque of PTO shaft. Lock the screw with the lock washer after adjusting the turning torque. Tightening torque Screw - 18.6 to 32 Nm (13.7 to 23.9 ft-lbs).

Differential Assembly

1.Shim, 2.Differential Side Gear, 3.Differential Pinion Collar, 4.Differential Pinion, 5.Thrust Collar, 6.Differential Side Gear, 7.Ring Gear Bushing, 8.Shim, 9.Differential Bearing Holder (RH), 10.Differential Side Shim, 11.Differential Pinion Shaft, 12.Differential Pinion Collar, 13.Differential Pinion, 14.Bearing, 15.Differential Case, 16.Ring Gear, 17.Bearing, 18.Differential Side Shim, 19.Differential Bearing Holder (LH)

Remove the left and right differential bearing holders (19), (9). Take out the differential assembly from the differential gear case. Install the differential assembly, noting the number of differential side shims (10), (18).

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