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Kubota B2620, B2630, B2920 - Hydrostatic Transmission

Kubota B2620, B2630, B2920 - Hydrostatic Transmission Components

1-Cylinder Block (Motor), 2-Piston, 3-Thrust Collar, 4-Motor Shaft, 5-Retainer Plate, 6-Thrust Collar, 7-Pump Shaft, 8-Variable Swashplate, 9-Piston, 10-Cylinder Block (Pump), 11-Charge Relief Valve, 12-Needle Bearing, 13-Valve Plate, 14-Check and High Pressure Relief Valve, 15-Neutral Valve

Kubota B2620, B2630, B2920 HST - Control Linkage

Cruise Control

1-Release Lever 1, 2-Cruise Release Rod, 3-Cruise holding Spring, 4-Cruise Control Lever, 5-Friction Plate, 6-Friction Disk, 7-Release Rod, 8-Neutral Holder, 9-Trunnion Shaft, 10-HST Pedal, 11-Control Lever Arm 2, 12-Cruise Control Base, 13-Cruise Rod, 14-HST Plate, 15-HST Lever, 16-Brake Pedal, 17-Return Spring, 18-Return Spring

Cruise control system mainly consists of cruise control lever holding section and cruise control releasing section. When the cruise control lever (4) is set to the desired position, the bottom end of the cruise control lever turns clockwise. The control lever (4) pushes the control lever arm 2 (11). The control lever arm 2 (11) pulls the cruise rod (13). The cruise rod (13) pulls the neutral holder (8). The HST plate (14) is pulled by the cruise rod (13). Since the neutral holder (8) turns clockwise, the trunnion shaft (9) directly attached to the neutral holder (8) turns clockwise. On the other hand, since the HST plate (14) pulls the HST lever (15) and the HST pedal (10). The HST pedal (10) is turned to the front side. On the other hand, since there is friction force between the friction plates (5) and the friction disks(6), the cruise control lever (4) is held at the desired cruise position until the brake pedals will be depressed by an operator.

Kubota B2620, B2630, B2920 Hydrostatic Transmission Troubleshooting

System Will Not Operate in Either Direction

Oil level is low - Check oil level or fill oil to proper level.
Speed control pedal linkage defective - Repair linkage.
Charge pressure is too low - Replace oil filter cartridge. Check charge pressure. Inspect or flush charge relief valve.
Check and high pressure relief valve doesn't move smoothly - Inspect/replace check and high pressure relief valve.
Neutral valve defective - Inspect or replace neutral valve.
Component parts defective - Replace hydrostatic transmission assembly.

Kubota B2620HST, B2630, B2920 Transmission Overheat

Low transmission oil level - Fill oil to proper level.
Radiator net clogged - Clean radiator net.
Excessive machine load - Reduce machine load
Improper charge pressure - Check high relief pressure. Replace transmission oil filter cartridge. Check and high pressure relief valve.

Machine Will not Stop in Neutral Position

Speed control linkage is out of adjustment or sticking - Repair or replace linkage. Adjust neutral adjuster.
Neutral valve defective - Inspect or replace neutral valve.

System Operates in One Direction Only

Speed control linkage defective - Repair or replace linkage.
Check and high pressure relief valve defective - Replace high pressure relief valve.

Noise From Front Case

Clutch shaft spline worn - Replace.
Bearing Worn - Replace.
Gear worn or broken - Replace.
Bi-Speed Turn clutch damaged - Replace.

Noise From Front Transmission

Transmission oil insufficient - Refill.
Gear worn or broken - Replace.
Improper backlash between spiral bevel pinon and bevel gear - Adjust.
Improper backlash between differential pinion and differential side gear - Adjust.
Bearings worn - Replace.
PTO clutch damaged - Repair or replace.

Kubota B2620, B2630, B2920 Tractor - Transmission Case

Checking Bearing

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.

Clearance between Shift Fork and Shift Gear Groove

Insert the fork into the shift gear groove and measure the clearance with a feeler gauge. If the clearance exceeds the allowable limit, replace it. Clearance between shift fork and shift gear groove - 0.10 to 0.35 mm (0.004 to 0.014 in). Allowable limit - 0.5 mm (0.020 in).

Backlash between Spiral Bevel Pinion and Spiral Bevel Gear

1 - Shim, 2 - Shim, 3 - Spiral Bevel Pinion, 4 - Bearing Holder, 5 - Shim, 6 - Spiral Bevel Gear, 7 - Shim

Set the dial indicator (lever type) with its finger on the end of spiral bevel pinion (3). Move the spiral bevel pinion back and forth to each end and measure the side clearance. If the side clearance exceeds the factory specifications, adjust with the shims (2) at front end of spiral bevel pinion. Set the dial indicator (lever type) with its finger on the tooth surface of bevel gear. Measure the backlash by fixing the spiral bevel pinion (2) and moving bevel gear (5) by hand. If the backlash exceeds the factory specifications, adjust with the shims (2), (7) at bearing holder (4) and differential case. Adjust the backlash properly by repeating the above procedure. Movement of spiral bevel pinion shaft at shaft directions - Approx. 0 mm (0 in). Backlash between spiral bevel pinion and spiral bevel gear - 0.10 to 0.30 mm (0.0039 to 0.0012 in). Thickness of shims (1) - 0.2 mm (0.008 in.) 1.4 mm (0.055 in.). Thickness of shims (5), (7) - 0.2 mm (0.008 in.) 0.5 mm (0.020 in.).

Kubota B2620HST, B2630, B2920 Tractor - PTO Clutch Case

Separating Differential case and PTO Clutch Case

Remove the transmission case mounting bolts. Separate the transmission case from the differential case. Remove the PTO brake plate 4 mounting bolt. Install the PTO brake plate 4 to the transmission case groove securely.

Bevel Pinion Shafts

Bevel Pinion Shaft 1 - Remove the bevel pinion shaft assembly from the transmission case. Remove the spacer. Install the spacer to the transmission case. Install the bevel pinion shaft assembly. Bevel Pinion Shaft 2 - Gear teeth number are changed by the tractor models. Check the gear teeth number and assemble the bevel pinion shaft assembly. B2620HST M/T (4WD/2WD) - 13T / 12T. B2630 (4WD/2WD) - 13T / 15T. B2920 (4WD/2WD) - 14T / 15T.

Range Gear Shaft Assembly

Remove the cir-clip from the range gear shaft. Remove the spring pin from the shift arm lever. Remove the range gear shaft assy and the fork rod from the transmission case.

Range Gear Shaft and Gears

Remove the ball bearing from the rang gear shaft. Remove the 12T gear, the 18T gear and the 26T gear. Install the range shift arm to the range shift fork securely. Install the O-rings to the range shift arm.

Front Wheel Drive Shaft

4WD Shaft - Remove the cir-clip from the 4WD shaft. Remove the 4WD gear from the 4WD shaft. Remove the 4WD shaft with the 26T gear. Remove the 26T gear and the ball bearing. 4WD Shaft Lever - Remove the bolt and the washer with rubber. Install the 4WD gear to the 4WD shaft. Install the 4WD shaft arm to the 4WD gear. Install the O-rings to the 4WD shift arm.

Rear PTO Shifter and Rear PTO Arm

Remove the rear PTO shifter from the PTO clutch shaft. Remove the spring pin from the rear PTO arm. Remove the PTO clutch shaft and the PTO shifter as an assembly. Install the rear PTO arm to the transmission case. After installing the PTO shifter to the PTO clutch shaft, install the rear PTO arm to the rear PTO shifter. Install the O-rings to the rear PTO arm. Install the PTO lever to the rear PTO arm. Install the spring pin to the rear PTO arm.

Installing PTO Shifter

Install the spring and the ball to the transmission. Push the ball by finger from the inside of the transmission case. Push the PTO shift arm ball guide into the transmission case. Push the PTO shift arm ball guide with the PTO shift arm. Install the PTO cotter to the PTO shift arm. Align the PTO cotter to the groove of the PTO shifter.

Kubota B2620, B2630, B2920 Transmission - Checking And Adjusting

Charge Pressure

Remove the lowering speed adjusting knob and the seat under cover. Remove the plug from reverse port or forward port. If the plug is tight to remove, warm up the plug by a hair driver etc. Install the adaptor to reverse port or forward port. Install the cable and low pressure gauge to the adaptor. Range gear shift position - Neutral. HST pedal - Neutral. Start the engine and warm the oil before testing. Change the range gear shift lever to "NEUTRAL" position. Run the engine at the rated speed. Release the foot from the HST pedal. Read the low pressure gauge to measure the charge relief pressure. If the measurement is not same as factory specification, check the charge relief valve and the related hydraulic components. Charge pressure - 0.4 to 0.6 MPa.

High Pressure Relief Valve Pressure (Reverse/Forward)

Remove the lowering speed adjusting knob and the seat under cover. Remove the plug from reverse/forward port. Install the adaptor to reverse/forward port. Install the cable and high pressure gauge. Range gear shift position - High. HST pedal - Reverse. Brake pedal - Depressed. Start the engine and warm the oil before testing. Check to see that parking brake is applied. Place the range gear shift lever to "HIGH" position. Run the engine at the rated speed. Depress the rear side pedal of the HST pedal. Read the high pressure gauge to measure the high pressure relief valve pressure. If the measurement is not the same as factory specification, check the check and high pressure relief valve assembly. Check and high pressure relief valve (Oil temperature at 40 to 60C) - 33.9 to 34.8 MPa.

Cruise Control Adjustment

Before adjusting the cruise control adjustment, adjust the brake pedal free travel securely. Brake pedal free travel - 30 to 40 mm (1.18 to 1.57 in.) on the pedal. Keep the free travel in the right and the left brake pedals equal. Check the cruise control is operated properly. The cruise control lever is returned to “OFF” position when depressing two brake pedals simultaneously. The cruise control lever is still kept at “ON” position when depressing one side brake pedal. If the cruise control is not operated properly as two conditions mentioned above, adjust the cruise control as follows. Depress the speed control pedal fully, and set the cruise control lever to “ON” position. Remove the rear wheel. When the cruise control lever is not returned to “OFF” position properly by depressing both brake pedals, after connecting both the left and the right brake pedals. Shorten the release rod until the cruise control is returned to “OFF” position. When the cruise control lever is not kept at “ON” position by depressing the one side brake pedal after disconnecting the brake pedal lock from the right brake pedal. Lengthen the release rod until the cruise control is kept at “ON” position. Release rod length (B2620, B2630 / B2930 - 534 mm (21.0 in) / 594 mm (23.4 in).

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