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Kubota B2230, B2320, B2530 - Hydrostatic Transmission

Kubota B2230, B2320, 2530 Tractor - HST Components

Hydrostatic Transmission (with Bi-Speed Turn Model): 1 - Hydrostatic Transmission (HST) Section, 2 - Hydrostatic PTO Section, 3 - Differential Gear Section, 4 - Rear PTO Gear Section, 5 - Range Gear Section, 6 - Mid-PTO Gear Section, 7 - Front Wheel Drive Gear Section, 8 - Bi-Speed Turn Gear Section, A - From Front Case, B - To Bi-Speed Turn Gear Section

Kubota B2230, B2320, 2530 Tractor - Bi-Speed Turn Powertrain

Bi-Speed Turn Engaged

1 - 30T Gear, 2 - 35T Gear, 3 - 28T-28T Front Wheel Drive Shaft 1, 4 - Bi-Speed Turn Clutch Case, 5 - Shifter, 6 - Piston, 7 - 23T Bi-Speed Turn Gear, 8 - Bi-Speed Turn Clutch Shaft (Front Wheel Drive Shaft 2), 9 - 24T Front Wheel Drive Shaft 3

When a operator engage the Bi-Speed Turn lever to “ON” position and the front wheel steering angle is above approximately 0.714 rad (42°), the Bi-Speed Turn engages. At the time, since both the Bi-Speed Turn valve 1 and the Bi-Speed Turn valve open, the pressured oil enter into the Bi-Speed Turn clutch shaft (8). The pressured oil push the piston in the Bi-Speed Turn clutch, and the shifter (5) connected to the piston (6) slides into the Bi-Speed Turn clutch pack. The shifter does not mesh to the 35T gear (2). The power is transmitted from the front wheel drive shaft 1 (28T-28T) (3) through the 23T Bi-Speed Turn gear (7), the Bi-Speed Turn clutch pack, and the shifter (5) to the Bi-Speed Turn clutch shaft (8), and to the 30T gear (1) and to the front drive shaft 3 (24T) (9).

Bi-Speed Turn Disengaged

1 - 30T Gear, 2 - 35T Gear, 3 - 28T-28T Front Wheel Drive Shaft 1, 4 - Bi-Speed Turn Clutch Case, 5 - Shifter, 6 - Piston, 7 - 23T Bi-Speed Turn Gear, 8 - Bi-Speed Turn Clutch Shaft (Front Wheel Drive Shaft 2), 9 - 24T Front Wheel Drive Shaft 3

When the front wheel steering angle is below 0.714 rad (42 °), the Bi-Speed Turn is disengaged. Since the pressurized oil is not delivered into the Bi-Speed Turn clutch pack, the shifter is pushed out to the 35T gear (2). The shifter meshes to the 35T gear (2). The power is transmitted as follows. Front wheel drive shaft (28T-28T) (3) - 35T gear (2) - shifter (5) - Bi-Speed Turn clutch shaft (8) - 30T gear (1) - front drive shaft (24T) (9).

Kubota B2230, B2320, 2530 HST - Control Linkage

1 - Neutral Arm, 2 - Roller, 3 - Neutral Holder, 4 - Trunnion Shaft, 5 - HST Pedal, 6 - Spring, 7 - Speed Control Rod (HST), 8 - Damper

The HST pedal (5) and the trunnion shaft (4) of the variable swashplate are linked with the speed control rod (7) and the neutral holder (3). As the front footrest of the HST pedal (5) is depressed, the swashplate rotates and forward travelling speed increases. Depressing the rear footrest increases reverse travelling speed. The roller (2) on the neutral holder arm (1) is held with spring seats and the detent of the neutral holder (3) so that the neutral holder (3) returns to neutral. When the pedal is released, the swashplate is returned to neutral with the neutral holder (3). The damper (8) connected to the HST pedal (5) restricts the movement of the linkage to prevent abrupt operation or reversing.

Front wheel drive section

Front wheel drive lever is located at the front floor cover. Front wheel drive lever and shifter are linked. 20T shifter gear is located on the front wheel drive shifter. 2-wheel drive or 4-wheel drive is selected by changing the position of 20T shifter gear reverse or forward. When the font wheel drive lever is set to "4 Wheel Drive Position", 20T shifter gear slides forward, meshes the13T gear on the 6T bevel pinion shaft. In this state, power from the 6T bevel pinion shaft is transmitted through 20T shifter gear to the front wheel drive shaft and the front wheels.

Kubota B2230, B2320, 2530 Tractor - PTO Clutch

1 - PTO Shift Lever, 2 - PTO Shift Arm, 3 - Rear PTO Arm, 4 - Rear PTO Control Plate, 5 - Control Rod, 6 - Independent PTO Clutch, 7 - PTO Position Selection Section, 8 - PTO shifter, 9 - 25T Mid PTO Gear, 10 - PTO Clutch Shaft, 11 - Rear PTO Rotation Prevention Section, 12 - Rear PTO shifter, 13 - 8T Rear PTO Shaft, 14 - Mid PTO Selection Section

The PTO shift lever (1) is located at left side fender. The PTO shift lever (1) and the PTO shift arm (2) are linked with the control rod (5).The PTO shift arm (2) and the rear PTO arm (3) linked with the rear PTO control plate. The PTO shift arm (2) shifts the PTO shifter (8). The rear PTO arm (3) shifts the rear PTO shifter (12). PTO gear section consists of four sections. The first section is independent PTO section. The second section is PTO position selection section. The third section is mid-PTO selection section. The fourth section is rear PTO rotation prevention section. In this section, when the PTO shift lever is set to "Mid-PTO" shifter slides to the front side and shifter meshes to the housing. The rear PTO shift does not rotate at this "Mid-PTO" position.

Kubota B2230, B2320, 2530 - Rear Axle

The rear axles are the semi floating type with ball bearing (2) between the rear axle (4) and the rear axle case (3), which supports the rear wheel load as well as transmitting power to the rear wheels. The differential gears (7) automatically control the revolution of right and left wheels when the rear wheels encounter unequal resistance during turning.

1 - Differential Gear Shaft, 2 - Ball Bearing, 3 - Rear Axle Case, 4 - Rear Axle, 5 - Spur Gear, 6 - Spiral Bevel Gear, 7 - Differential Gear

Removing Rear Wheels and Rear Axle

Support the tractor sub-frame with a jack. Remove the snap pin and the pin. Loosen and remove the nut. Remove the spring washer and the bolt. Remove the rear wheel from the rear axle.

Kubota B2230, B2320, 2530 - Transmission Disassembling And Assembling

Front Case Assembly

Support the engine securely. Remove the front case mounting bolts. Remove the front case from the frame. Apply liquid gasket to the joint face of the engine and the front case.

Clutch Shaft and Ball Bearing

Remove the oil seal. Remove the cir-clip. Remove the clutch shaft from the front case.

Steel Plate

Remove the steel plate mounting bolts. Remove the steel plate from the flywheel. Apply liquid gasket to the joint face of the engine and the front case.

Bi-Speed Turn ON-OFF Valve and Front Case Rear Cover

Remove the Bi-Speed Turn rod 1, the Bi-Speed Turn ON-OFF valve and the Bi-Speed Turn Valve. Remove the connecting pipe. Remove the front case rear cover mounting bolts and the front case rear cover. Check the oil seals and the O-ring for damage.

Bi-Speed Turn Clutch Assembly and Front Wheel Drive Shaft 1

Remove the clutch shaft 1, the front wheel drive shaft 1 and Bi-Speed Turn clutch shaft from the front case. Remove the internal cir-clip. Remove the front wheel drive shaft 3 with the bearing holder.

Disassembling Bi-Speed Turn Clutch Assembly 1

Remove the bearings. Remove the 30T gear, the 35T gear and the cir-clip. Remove the bearing. Remove the thrust collar and the 23T gear. Check the seal ring for damage.

Disassembling Bi-Speed Turn Clutch Assembly 2

Remove the Bi-Speed Turn clutch shaft. Loosen and remove the flange nuts. Remove the shifter. Remove the cir-clip with the special tools. Remove the internal cir-clip. Remove the clutch disks and the plates. Check the seal ring for damage. Tighten the flange nuts to the specified tightening torque.

Kubota B2230, B2320, 2530 HST - Main Gear Shift Section

Steps, Brake Rods, Hydraulic Pipes, Sub-Frames and Wiring Harness

Remove the steps and the brake springs. Disconnect the connectors from the HST neutral switch, the PTO switch and the PTO valve switch. Move the wiring harness to the engine side. Disconnect the hydraulic suction pipe and the hydraulic delivery pipes. Loosen the pipe bands. Remove the snap pins and disconnect the brake rods. Remove the sub-frame mounting bolts and the sub-frames. Hook the transmission assembly. Remove the main frame mounting bolts and the main frame. Separate the transmission assembly from the tractor main frame. Remove the spring pins from the propeller shaft. Connection of couplings - Set the rear wheels to the tractor. Firstly install the coupling between the front axle pinion shaft and the front wheel drive shaft under the engine. Install the coupling and the propeller shaft to the clutch shaft. Secondly align the spline between the front wheel drive shaft and the universal joint. Thirdly, push the transmission assembly slowly to the main frame side, and align the spline between propeller shaft and the first shift shaft. Align the universal joint and the front wheel drive shaft. Fourthly, install the split pins from the down side.

Separating Main Gear Shift Section Assembly

Remove the propeller shaft. Remove the spring pins. Remove the main gear shift section mounting bolts and the nuts. Separate the main gear shift section case assembly from the transmission case. Apply the liquid gasket. Align the coupling spline between the shuttle shaft and the Hi-Lo gear shaft. Align the coupling spline between the front wheel drive shafts.

Removing Mechanical PTO Clutch Cam and Bearing Holder

Remove the cir-clip. Remove the one way clutch cam, the one way clutch spring and the collar. Remove the bearing holder mounting bolts. Remove the bearing holder. Install the spacer to the bearing.

Removing Main Gear Shift Shafts

Remove the shim with the bearing holder. Remove the shuttle switch. Remove the shuttle shaft, the shift shaft 2, the front wheel drive shaft and the shift shaft 1 temporally. Remove the bearing from the front wheel drive shaft. Install the bearing to the main gear shift (section) case. Install the shuttle shifter and the shuttle shaft to the main gear shift (section) case. Install the three shafts, the shift shaft 1, the shift shaft 2 and the shuttle shaft to the main gear shift (section) case and install the front wheel drive shaft to the bearing simultaneously shaking all shafts slowly. Check the four shafts to rotate smoothly. Install the shim to the bearing hole for the shuttle shaft.

Kubota B2230, B2320, 2530 - Mid-PTO Section

Mid-Gear and Idle Shaft (Mid-PTO Model)

Remove the idle shaft from the transmission case using a screw driver. Remove the mid-gear from the transmission case. Remove the ball bearings and the internal cir-clip from the mid-gear. Install the internal cir-clip to the inner groove of the mid-gear securely.

Mid-PTO Case and Mid-gear Shaft (Mid-PTO Model)

Remove the mid-PTO case mounting bolts. Remove the mid-PTO case from the transmission case. Remove the mid-PTO oil seal from the mid-PTO case using a screw driver not to damage it. Remove the internal cir-clip. Remove the mid-gear shaft with the ball bearings. Remove the bearing from the mid-gear shaft. If the mid-PTO oil seal is defective, worn or scratched, replace it. Apply grease to the lip and the outer of the mid-PTO oil seal. Apply liquid gasket to the joint surface A of the transmission case and the mid-PTO case.

Kubota B2230, B2320, 2530 - Transmission Case

Differential Gear

Clearance between Differential Case (Spiral Bevel Gear) and Differential Side Gear Measure the differential side gear boss O.D. with an outside micrometer. Measure the differential case I.D. and the spiral bevel gear I.D. with an inside micrometer, and calculate the clearance. If the clearance exceeds the allowable limit, replace faulty parts. Clearance between differential case (spiral bevel gear) and differential side gear - 0.025 to 0.066 mm (0.0010 to 0.0025 in). Allowable limit - 0.30 mm (0.0118 in). Differential case I.D. - 32.000 to 32.025 mm (1.2599 to 1.2608 in). Spiral bevel gear I.D. - 32.000 to 32.025 mm (1.2599 to 1.2608 in). Differential side gear O.D. - 31.959 to 31.975 mm (1.2582 to 1.2589 in).

Clearance between Differential Pinion Shaft and Differential Pinion

Measure the differential pinion shaft O.D. with an outside micrometer. Measure the differential pinion I.D. with an inside micrometer, and calculate the clearance. If the clearance exceeds the allowable limit, replace faulty parts. Clearance between differential pinion shaft and differential pinion - 0.016 to 0.045 mm (0.0007 to 0.0018 in). Allowable limit - 0.30 mm (0.0118 in). Differential pinion I.D. - 16.000 to 16.018 mm (0.6300 to 0.6306 in). Differential pinion shaft O.D. - 15.973 to 15.984 mm (0.6289 to 0.6292 in).

Backlash between Differential Pinion and Differential Side Gear

Secure the differential case with a vise. Set the dial indicator (lever type) with its finger on the tooth of the differential side gear. Press differential pinion and side gear against the differential case. Hold the differential pinion and move the differential side gear to measure the backlash. If the backlash exceeds the allowable limit, adjust with differential side gear shims. Backlash between differential pinion and differential side gear - 0.1 to 0.3 mm (0.004 to 0.011 in). Allowable limit - 0.4 mm (0.016 in). Thickness of shims: 0.80 mm (0.0315 in.) / 1.00 mm (0.0394 in.) / 1.20 mm (0.0472 in.).

Differential Gear Section

Separating Hydraulic Cylinder, Transmission Case and Rear Axles

Remove the hydraulic cylinder as an assembly. Separate the transmission case. Separate the rear axles.

Rear-PTO Case and Rear PTO Shaft

Remove the rear PTO cover mounting bolts and the rear PTO cover. Apply liquid gasket to the joint surface of the rear axles cases and the rear PTO cover.

Differential Bearing Holder (RH)

Remove the differential holder mounting bolts. Remove the differential holder and shims. 0.5 mm (0.020 in.) shim, 0.2 mm (0.008 in.) shim.

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