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Kubota BX23, BX23S, BX24, BX25, BX25D Transaxle - Disassembling and service

Kubota BX23, BX23S, BX24, BX25, BX25D - Separating transaxle

Draining transmission fluid

Place oil pan under the tractor. Remove the drain plug at the bottom of the transmission case. Drain the transmission fluid and reinstall the drain plug. Do not operate the Kubota BX23, BX23S, BX24, BX25, BX25D tractor immediately after changing the transmission fluid. Operate the engine at medium speed for a few minutes to prevent damage to the transmission. Do not mix different brands oil together. Fill new oil from filling port after removing the filling plug up to the upper notch on the dipstick. After operating the engine for few minutes, stop it and check the oil level again, if low, add oil to prescribed level. Transmission fluid Capacity - 11.6 L. Removing battery, lift rod and lower link, rear wheel, ROPS and seat - Remove the under panel. Disconnect the negative cable from the battery. Disconnect the positive cable from the battery and remove the battery.

Removing lift rod and lower link

Remove the top link. Remove the stopper pin and remove the check chain plate. Move the bushes to inside. Move the shaft to right side and remove the lower link as a unit. Removing ROPS and seat - Disconnect the R.H and L.H. hazard lamp/turn signals from the wire harness. Remove the upper ROPS. Remove the ROPS mounting bolts. Remove the R.H. and L.H. lower ROPS. Tightening torque ROPS mounting bolt - 48.0 to 55.9 Nm / 35.5 to 41.2 lbf-ft. Disconnect the seat switch connectors. Remove the snap pins to remove the seat.

Removing step and fender

Disconnect the upper cruise control rod from the lower cruise control rod. Remove the R.H. and L.H. side covers. Remove the step mat. Remove the forward and reverse HST pedals. Remove the step. Disconnect the L.H. and R.H. tail lamps from the wire harness. Disconnect the 12 V outlet from the wire harness. 12 V outlet connector is near the L.H. tail lamp connector. Remove the L.H. lever grips. Remove the differential lock pedal cover, cutting height adjusting dial knob, and lower speed adjusting knob. Remove the R.H. lever grips. Remove the R.H. lever guide and R.H. handrail. Remove the L.H. lever guide stay nut. Remove the fender.

Removing fuel tank

Remove the and R.H. lever guide stay. Drain the fuel from the fuel tank. Disconnect the fuel sensor connectors and safety switch connector. Remove the fuel tube cover. Disconnect the fuel return hose and fuel supply hose. Remove the seat stopper. Remove the R.H. and L.H. fuel tank stays and cushions, then remove the fuel tank. Fuel tank stay mounting bolt and nut - 48 to 55 Nm. Seat stopper bolts - 123.5 to 147.0 Nm / 91.2 to 108 lbf-ft.

Removing fender center stay, fender bracket and hitch plate

Remove the fender center stay. Fender center stay mounting bolt and nut (M14) - 98.0 to 125 Nm / 79.6 to 92.5 lbf-ft. Fender center stay mounting bolt and nut (M10) - 39.2 to 45.1 Nm / 29.0 to 33.2 lbf-ft. Remove the hitch plate. Remove the parking brake return spring and the fender brackets. Do not firmly tighten all screws, bolts and nuts until most components are attached. Hitch plate mounting bolt and nut (M14) - 124 to 147 Nm / 91.2 to 108 lbf-ft. Fender bracket mounting bolt and nut (M14) - 124 to 147 Nm / 91.2 to 108 lbf-ft.

Kubota BX23, BX23S, BX24, BX25, BX25D - Removing transaxle assembly

Remove the differential lock rod and disconnect the mower link. Remove the brake rod. Disconnect the hoses. Disconnect the connectors. Remove the rear coupling mounting bolt. Disconnect the power steering pipes from the transaxle. Remove the speed control rod. Remove the wire harness clamps. Remove the frame brackets. Speed control rod length - 373 mm / 14.7 in. Tighten the smaller bolt (M12) first. Before mounting the transaxle assembly on the Kubota BX23, BX23S, BX24, BX25, BX25D tractor main frame, check the flatness of the frame brackets with a straight edge securely. Transaxle assembly mounting bolt (M12) - 63 to 72 Nm / 47 to 53 lbf-ft. Transaxle assembly mounting bolt (M14) - 124 to 147 Nm / 91.2 to 108 lbf-ft. Rear coupling mounting bolt (M8) - 24 to 27 Nm / 18 to 20 lbf-ft. Removing brake pedal - Unhook the spring and remove the parking lock. Remove the split pin then remove pin from the brake arm. Remove the brake pedal.

Removing propeller shaft

Disconnect the front coupling from the engine. Remove the propeller shaft assembly. Remove the HST fan from the propeller shaft. Apply grease to inside of the front coupling and the rear coupling. Front coupling mounting bolt (M8) - 24 to 27 Nm / 18 to 20 lbf-ft. HST fan mounting bolt (M8) - 9.8 to 11 Nm / 7.3 to 8.6 lbf-ft. Removing differential lock pedal - Remove the differential lock return spring. Remove the rue ring cotter. Turn and remove the differential lock pedal. Removing speed control pedal, HST damper, and cruise rod - Remove the speed control pedal. Remove the rue ring cotter. Remove the HST dumper. Remove the cruise arm. Remove the cruise rod. Remove the spring pin then remove the release arm and cruise plate.

Kubota BX23, BX23S, BX24, BX25, BX25D - Transaxle case

Checking bearing

Hold the inner race, and push and pull the outer race in all directions to check wear and roughness. Apply the transmission oil to the bearing, and hold the inner race. Turn the outer race to check rotation. If there are any damaged, replace the bearing. Checking flatness of actuator and bearing holder - Place a straightedge on the contacting surface of the actuator and the bearing holder. Inspect the friction surface of the actuator and the bearing holder with the straightedge, and determine if a feeler gauge will fit on the part of wear. Flatness of actuator and bearing holder (Kubota BX23, BX23S, BX24, BX25, BX25D) - 0.30 mm / 0.012 in. If it will fit, resurface.

Kubota BX23, BX23S, BX24, BX25, BX25D - Checking PTO clutch

Checking PTO clutch disc wear - Measure the thickness of PTO clutch disc with vernier calipers. If the thickness is less than the allowable limit, replace it. Thickness of PTO clutch disc - 1.50 to 1.70 mm / 0.0591 to 0.0669 in. Checking flatness of clutch piston, pressure plate and steel plate - Place the part on a surface plate. Check the flatness by inserting a feeler gauge (allowable limit size) underneath it at least four points. Flatness of clutch piston - 0.15 mm / 0.0059 in. Flatness of pressure plate and steel plate - 0.20 mm / 0.0079 in. If the gauge can be inserted, replace it. Checking clutch spring free length - Measure the free length of spring with vernier calipers. If the measurement is less than the allowable limit, replace it. Clutch spring free length - 38.5 mm / 1.52 in.

Kubota BX23, BX23S, BX24, BX25, BX25D - Checking brake

Checking PTO brake disc wear - Measure the PTO brake disc thickness with a vernier caliper. If the thickness is less than allowable limit, replace it. PTO brake disc thickness - 2.90 to 3.10 mm / 0.115 to 0.122 in. Checking PTO brake plate - Measure the PTO brake plate thickness with a vernier caliper. If the thickness is less than allowable limit, replace it. PTO brake plate thickness - 1.9 to 2.1 mm / 0.075 to 0.082 in. Checking brake cam lever movement - Move the brake cam lever by hand to check its movement. If its movement is heavy, refine the brake cam with a emery paper.

Checking brake disc and friction plate wear

Measure the brake disc thickness and the friction plate thickness with an outside micrometer. If the thickness is less than the allowable limit, replace it. Brake disc thickness - 3.30 to 3.50 mm / 0.130 to 0.137 in. Friction plate thickness - 1.92 to 2.08 mm / 0.0756 to 0.0818 in. Checking separate plate and back plate wear - Measure the thickness of pressure plate and steel back with vernier calipers. If the thickness is less than the allowable limit, replace it. Thickness of separate plate - 0.9450 to 1.055 mm / 0.03721 to 0.04153 in. Thickness of back plate - 1.9 to 2.1 mm / 0.075 to 0.082 in.

Checking height of cam plate and ball

Measure the height of the cam plate with the ball installed. If the measurement is less than the allowable limit, replace the cam plate and balls. Height of cam plate and ball - 22.89 to 22.99 mm / 0.9012 to 0.9051 in. Inspect the ball holes of cam plate for uneven wear. If the uneven wear is found, replace it.

Checking clearance

Checking clearance between differential case and differential side gear (Kubota BX23, BX23S, BX24, BX25, BX25D) - Measure the differential side gear boss O.D. with an outside micrometer. Differential side gear O.D - 37.911 to 37.950 mm / 1.4926 to 1.4940 in. Measure the differential case I.D. with a cylinder gauge and calculate the clearance. Differential case I.D - 38.000 to 38.062 mm / 1.4961 to 1.4985 in. If the clearance exceeds the allowable limit, replace damaged parts. Clearance between differential case and differential side gear - 0.0500 to 0.151 mm / 0.00197 to 0.00594 in.

Checking clearance between differential pinion shaft and differential pinion - Measure the differential pinion shaft O.D. with an outside micrometer. Differential pinion shaft O.D. - 19.959 to 19.980 mm / 0.78579 to 0.78661 in. Measure the differential pinion I.D. with a cylinder gauge, and calculate the clearance. Differential pinion I.D - 20.060 to 20.081 mm / 0.78977 to 0.79059 in. If the clearance exceeds the allowable limit, replace damaged parts. Clearance between differential pinion shaft and differential pinion - 0.0800 to 0.122 mm / 0.00315 to 0.00480 in.

Checking backlash

Checking 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 it with differential side gear shims. Backlash between differential pinion and differential side gear - 0.15 to 0.30 mm / 0.0059 to 0.011 in. Thickness of shims - 1.5 mm / 0.059 in.

Checking backlash between spiral bevel pinion gear and bevel gear - Temporarily assemble the spiral bevel pinion gear and the bevel gear in the transaxle case. Hold the wire of solder or plastigauge on the bevel gear teeth upper surface. Turn the front drive shaft one turn clockwise by hands. Measure the backlash between the spiral bevel pinion gear and the bevel gear. If the backlash exceeds the factory specifications, adjust the shims. Backlash between spiral bevel pinion and bevel gear - 0.10 to 0.30 mm / 0.0040 to 0.011 in.