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Kubota BX1870, BX2370, BX2670 - Transmission Service

Kubota BX1870, BX2370, BX2670 Hydrostatic Transmission - Checking And Adjusting

Adjustment of HST Neutral Position

1 - Range Gear Shift Lever, 2 - Front Wheel Drive, 3 - Speed Control Pedal, 4 - Neutral Adjust Lever, 5 - Locking Screw, 6 - Screw Driver, A - 4WD OFF Position, B - Hi Position

Start the engine. Keep the engine at the maximum revolution. Shift the range shift lever (1) to “Hi” position (B). Loosen the locking screw (5). When adjusting the HST neutral position, loosen the locking screw approximately 2 turns counterclockwise not to drop the nut inside. Make sure 4WD lever is set to 2WD before making adjustment. Forward to Neutral Position - Depress the speed control pedal (3) to “Forward” speed position, and release the foot from the speed control pedal (3). Check that the rear axle (or the wheel) stops rotating. If the rear axle (or the wheel) does not stop rotating, move the position of the locking screw (5) to the machine front side to stop rotating. Reverse to Neutral Position - Depress the speed control pedal (3) to “Reverse” speed position, and release the foot from the speed control pedal (3). Check the rear axle (or the wheel) stops rotating. If the rear axle (or the wheel) does not stop rotating, adjust the locking screw (5) to stop rotating. After adjusting the neutral position, tighten the lock screw (5) securely.

Charge Relief Pressure

Remove the plug (R 1/4) from the front cover, then install the adaptor (R 1/4) and pressure gauge. Set the range gear shift lever to “Neutral” position. Start the engine and run it at the maximum speed. Read the pressure gauge to measure the charge relief pressure. If the measurement is not within the factory specifications, check the charge relief valve and related hydraulic components. Charge relief pressure (Oil temperature at 50C) - 0.55 to 0.75 MPa (80 to 100 psi).

PTO Clutch Operating Pressure

Lift the rear of the tractor and remove the left rear wheel. Remove the plug (R 1/8), then install the adaptor (R 1/8), cable and pressure gauge. Start the engine and set at maximum speed. Move the PTO clutch lever to “Engaged” position, and measure the pressure. If the measurement is not same as factory specifications, check the PTO relief valve and related hydraulic components. PTO clutch operating pressure - 1.0 to 1.3 MPa (150 to 180 psi).

Kubota BX1870, BX2370, BX2670 - Hydrostatic Transmission Service

Removing hydrostatic transmission case front cover

1. 4WD detent bolt, 2. Detent spring, 3. Detent ball, 4. Transaxle case front cover, 5. Circlip, 6. HST pump shaft (PTO shaft), 7. Front cover mounting bolt, 8. Front wheel drive shaft, 9. Spiral bevel pinion shaft, 10. HST motor shaft, 11. Mid-PTO shaft, 12. Mid-PTO idle gear shaft, 13. PTO select shaft

Before removing the transaxle case front cover (4), remove the 4WD detent bolt (1), the detent spring (2) and the detent ball (3) from the transaxle case front cover (4). Remove the circlip (5) from the hydrostatic transmission pump shaft (PTO shaft) (6) and the HST motor shaft securely. Remove the transaxle case front cover mounting bolts (7). Remove the transaxle case front cover (4) as an unit. Apply liquid gasket to the joint surface of the transaxle case to the front cover.

Removing hydraulic pump assembly

Remove the hydraulic pump assembly mounting bolt. Remove the hydraulic pump assembly as an unit from the transaxle case. Apply transmission oil to the O-rings. Since the mounting bolt is installed through the hydraulic pump to the transaxle case, bind the sealing tape to the mounting bolt securely.

Removing rear PTO cover assembly

1 - Bolt, 2 - Rear PTO cover, 3 - Bearing, 4 - 11T PTO select shaft, 5 - Rear PTO shaft, 6 - Oil seal, 7 - Vinyl tape

Remove the rear PTO cover mounting bolts. Remove the rear PTO cover. Remove the rear PTO shaft from the rear PTO cover. Pull the 11T PTO select shaft with the bearing approximately the bearing thickness. Apply liquid gasket to the joint surface of transaxle case to the rear PTO cover. Bind the vinyl tape to the rear PTO shaft not to damage the oil seal.

Kubota BX1870, BX2370, BX2670 - Removing PTO clutch assembly

1 - Pump shaft (PTO clutch shaft), 2 - Bearing, 3 - Clutch gear, 4 - Clutch pack, 5 - Bearing, 6 - Seal ring, 7 - Clutch case, 8 - O-ring, 9 - Brake disc, 10 - Brake plate, 11 - Clutch piston, 12 - Separate plate, 13 - Disc plate, 14 - Backing plate, 15 - Internal circlip, 16 - Brake spring, 17 - Washer, 18 - External circlip, 19 - Clutch spring compressor

Remove the bearing (2). Remove the external circlip and the clutch gear (3). Remove the seal rings (6). Remove the bearing (5). Remove the external circlip (18) using a clutch spring compressor. Disassembling the clutch pack inner parts as show in the figure. Change the seal rings (6) with a new one.

Check and high pressure relief valve checking

Check and high pressure relief valve (reverse) has a pin hole. Pin hole (Factory specification) - 1.5 mm / 0.059 in. Check the check and high pressure relief valve for scratches and damage. Check the spring for breakage and wear. If anything are unusual, replace the check and high pressure relief valve as complete assembly.

Checking cylinder block assembly

Do not interchange the pistons between the pump cylinder block and the motor cylinder block. Pistons and cylinder blocks are matched. Check the cylinder blocks and the pistons for scratches and wear. If there are scratch or worn, replace the cylinder block assembly. Check the pistons for their free movement in the cylinder block bores. If the piston or the cylinder block is scored, replace the cylinder block assembly. Check the polished face of the cylinder block for scoring. If it is scored, replace the cylinder block assembly.

Kubota BX1870, BX2370, BX2670 Transmission Problems

Vibration and Noise

Oil level is too 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.
Defective component parts - Replace hydrostatic transmission assembly.

Loss of Power

Low oil level - Add oil in hydrostatic transmission.
Low charge pressure - Replace oil filter cartridge. Checking charge pressure. Repair the charge relief valve.
Component parts are worn - Check and repair hydrostatic transmission components.

Transmission Oil Overheats

Transmission oil level is low - Fill transmission oil level up to proper level.
Radiator net clogged - Clean radiator net.
Excessive machine load - Reduce machine load.
Improper charge pressure - Check high relief pressure. Change transmission oil filter cartridge. Inspect and change the relief valve.

Noise from Transmission

Transmission oil insufficient - Refill.
Gear worn or broken - Check and replace.
Bearings worn - Change defective parts.

Gear Slip Out of Mesh

Shift fork spring tension insufficient - Replace defective parts.
Shift fork or shifter worn - Change damage parts.
Shift fork bent - Replace.

Differential Lock Can Not Be Set

Differential lock shift fork damaged - Replace.
Differential lock shifter mounting pin damaged - Replace.
Differential lock pin damaged - Replace.

PTO Clutch Operating Pressure is Low

Transmission oil improper or insufficient - Replenish or change.
Relief valve malfunctioning - Check or replace.

Kubota BX1870, BX2370, BX2670 Transmission - Servicing Specifications

Item	Factory Specification	Allowable Limit
Charge Relief Valve Setting Pressure	0.55 to 0.75 MPa (80 to 100 psi)	-
High Pressure Relief Valve (F/R) Setting Pressure	20.1 to 21.1 MPa (2920 to 3060 psi)	-
PTO Clutch Operating Pressure	1.0 to 1.3 MPa (150 to 180 psi)	-
PTO Clutch Disc Thickness	1.50 to 1.70 mm (0.0591 to 0.0669 in)	1.35 mm (0.0531 in)
Separate Plate Thickness	0.945 to 1.055 mm (0.0372 to 0.0415 in)	0.80 mm (0.031 in)
Back Plate Thickness	1.9 to 2.1 mm (0.075 to 0.082 in)	1.85 mm (0.0728 in)
Clutch Piston Flatness	-	0.15 mm (0.0059 in)
Pressure Plate and Steel Plate Flatness	-	0.20 mm (0.0079 in)
Clutch Spring Free Length	38.5 mm (1.52 in)	34.5 mm (1.36 in)
PTO Brake Disc Thickness	2.90 to 3.10 mm (0.115 to 0.122 in)	2.70 mm (0.11 in)
PTO Brake Plate Thickness	1.9 to 2.1 mm (0.075 to 0.082 in)	1.85 mm (0.073 in)
Differential Case / Differential Side Gear Clearance	0.05 to 0.151 mm (0.00197 to 0.00594)	0.30 mm (0.012 in)
Differential Case I.D.	38.0 to 38.062 mm (1.4961 to 1.4985 in)	-
Differential Side Gear O.D.	37.911 to 37.95 mm (1.4926 to 1.4940 in)	-
Differential Pinion Shaft / Differential Pinion Clearance	0.08 to 0.122 mm (0.00315 to 0.0048 in)	0.30 mm (0.012 in)
Differential Pinion I.D.	20.06 to 20.08 mm (0.78977 to 0.7906 in)	-
Differential Pinion Shaft O.D.	19.96 to 19.98 mm (0.78579 to 0.7866 in)	-
Differential Pinion to Differential Side Gear Backlash	0.15 to 0.30 mm (0.0059 to 0.011 in)	0.40 mm (0.016 in)
Spiral Bevel Pinion Shaft / Spiral Bevel Gear Backlash	0.10 to 0.30 mm (0.0040 to 0.011 in)	-
Actuator and Bearing Holder Flatness	-	0.30 mm (0.012 in)
Cam Plate and Ball Height	22.89 to 22.99 mm (0.9012 to 0.9051 in)	22.40 mm (0.8819 in)
Brake Disc Thickness	3.30 to 3.50 mm (0.130 to 0.137 in)	3.0 mm (0.12 in)
Friction Plate Thickness	1.92 to 2.08 mm (0.0756 to 0.0818 in)	1.52 mm (0.0598 in)

Item	Tightening torque
Charge relief valve checking plug (R 1/4)	30 to 44 Nm (22 to 32 lbf-ft)
Hexagon socket head plug (R 1/4)	30 to 44 Nm (22 to 32 lbf-ft)
Check and high pressure valve screw	25 to 29 Nm (18 to 21 lbf-ft)
PTO clutch operating pressure plug (R 1/8)	13 to 21 Nm (9.4 to 15 lbf-ft)
ROPS mounting nut	124 to 147 Nm (91.2 to 108 lbf-ft)
Fuel tank stay mounting bolt and nut	48 to 55 Nm (36 to 41 lbf-ft)
Fender bracket mounting bolt and nut	147 Nm (91.2 to 108 lbf-ft)
Rear wheel mounting screw	109 to 129 Nm (80.3 to 95.4 lbf-ft)
Hitch plate mounting bolt and nut	124 to 147 Nm (91.2 to 108 lbf-ft)
Transaxle assembly mounting screw (M12)	63 to 72 Nm (47 to 53 lbf-ft)
Transaxle assembly mounting screw (M14)	124 to 147 Nm (91.2 to 108 lbf-ft)
Rear coupling mounting screw (M8)	24 to 27 Nm (18 to 20 lbf-ft)
Front coupling mounting screw (M8)	24 to 27 Nm (18 to 20 lbf-ft)
Hydrostatic transmission fan mounting screw (M8)	9.8 to 11 Nm (7.3 to 8.6 lbf-ft)
Hydraulic control lever mounting bolt and nut	18 to 20 Nm (13 to 15 lbf-ft)
HST front cover mounting bolt and nut	18 to 20 Nm (13 to 15 lbf-ft)
Check and High pressure relief valve plug	59 to 78 Nm (44 to 57 lbf-ft)
Hydraulic cylinder mounting screw	40 to 44 Nm (29 to 32 lbf-ft)
Transmission case front cover mounting bolt (M8)	30 to 34 Nm (22 to 25 lbf-ft)
Hydraulic pump assembly mounting bolt (M6)	7.9 to 8.8 Nm (5.8 to 6.5 lbf-ft)
Hydraulic pump assembly mounting bolt (M8)	18 to 20 Nm (13 to 15 lbf-ft)
Rear PTO cover mounting bolt (M8)	18 to 20 Nm (13 to 15 lbf-ft)
Rear axle case (RH) mounting bolt (M8)	18 to 20 Nm (13 to 15 lbf-ft)
66T final gear mounting screw	61 to 70 Nm (45 to 52 lbf-ft)

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