1. The loader is weak or not moving in one gear, while other gears are normal.

Key points for diagnosis:

When not moving or moving slowly, the main drive shaft rotates quickly and powerfully. When the engine speed is increased, the increase in main drive shaft speed is significantly disproportionate to the increase in front and rear drive shaft speeds.

The transmission oil pressure is normal in neutral and other gears, but the pressure drops significantly after engaging this gear.

Possible causes:

1) Severe wear of the bearing cap or nylon ring.

2) If the bearing cap or nylon ring is in good condition or only slightly worn, then the clutch's inner and outer sealing rings for that gear are faulty.

Troubleshooting:

Replace the corresponding damaged parts, i.e., the bearing cap or nylon ring, and the inner and outer sealing rings. Readjust the clearance between the bushing and the bearing cap.

Fault analysis: Weak or no movement in one gear eliminates problems with the torque converter, travel pump, pressure reducing valve, and other common oil circuits and components for each gear. The fault must lie in the oil circuit between the transmission control valve and the clutch piston for that gear. 1. Wear of weak components such as the bearing cap, nylon ring, and inner and outer sealing rings causes significant oil leakage from the worn areas, resulting in reduced oil pressure. When in neutral or other gears, the oil pressure appears normal because the oil does not flow through the worn areas.

2. The machine moves automatically in neutral and continues to move normally when engaged in forward gear. However, the machine stops and cannot move when engaged in reverse gear. The operating pressure in all gears is normal.

Possible Causes:

The driving and driven plates of the forward clutch are seized and locked.

The forward clutch piston is stuck, or the support check valve is blocked.

Troubleshooting:

Disassemble the forward clutch, clean the oil passages, replace the driving and driven friction plates and related damaged parts, clean all relevant parts, replace the outer sealing ring, clean and unclog the check valve, and replace the clutch friction plates and inner and outer sealing rings.

3. During normal operation, the machine suddenly stops working after engaging second gear. The operating pressure in this gear and all other gears is normal.

Cause of failure:

The clutch shaft for this gear is broken.

Troubleshooting:

Replace the clutch shaft and readjust the bearing clearance.

4. The machine suddenly stops moving forward and backward while running, but the transmission pressure is normal.

Fault Causes:

1) Faulty transmission distribution valve or damaged accumulator (40F, 50D, 50F); stuck or damaged transmission valve pneumatic control valve stem.

2) Blocked oil inlet.

3) Blocked accumulator oil circuit.

4) Failed pneumatic control shut-off valve.

Troubleshooting:

Clean the transmission valve isolation valve stem or replace the pneumatic control valve; clear all relevant oil circuits; repair or replace the pneumatic control shut-off valve.

5. If the machine is working normally but suddenly loses steering, lifting, and movement, it indicates a damaged elastic connecting plate or worn teeth on the connecting wheel.

Fault Causes:

Broken elastic connecting plate; damaged elastic connecting plate fixing bolts; worn teeth on the connecting wheel.

Troubleshooting:

Replace the elastic connecting plate; replace the connecting wheel.

6. The transmission working pressure is normal; when the machine is under heavy load, the main drive shaft rotates quickly and powerfully. The machine malfunctions during digging operations and contains metallurgical powder in the transmission fluid.

Possible causes:

High/low speed control lever not in the low speed position or transmission valve not properly engaged; 1:3 clutch damaged; forward clutch damaged.

Solutions:

Engage the high/low speed lever to the low speed position and readjust the lever.

Replace the clutch friction plates and any damaged components.

7. Oil leakage from the torque converter top breather.

Possible causes:

Transmission valve pneumatic control valve stem "O" ring or leak; torque converter return oil filter clogged; torque converter internal oil passage or guide wheel seat oil passage clogged; torque converter to gearbox return oil line clogged.

Solutions:

Replace the pneumatic control valve "O" ring; clean or replace the return oil filter; clean all oil passages or replace the guide wheel seat; clean or... Replace oil pipes

8. Abnormal noise from the torque converter

Possible causes:

Damaged torque converter connecting gears or rubber teeth; cracked torque converter flexible connecting plate; damaged main/driven gear shafts or bearings in 30F/30D torque converters; mismatched splines on the main drive shaft or excessive clearance in the universal joint bearings.

Solutions:

Replace the connecting wheel or rubber teeth; replace the flexible connecting plate; replace the main/driven gears or bearings; readjust or adjust the clearances.

9. Machine operates normally, but oil temperature is high, output power is insufficient, and there is aluminum shavings in the transmission fluid.

Possible causes:

Clogged return oil filter; clogged machine oil cooler; blocked return oil line; damaged bearings; worn torque converter three-wheel drive.

Solutions:

Clean or replace the filter element; replace the cooler; clean and unclog all oil lines or replace... Replace bearings, replace three wheels and adjust clearance.

10. Low-speed or high-speed disengagement

Causes:

Excessive clearance in the control mechanism or improper adjustment of the linkage; wear of the sliding sleeve and high/low speed gears, insufficient meshing; excessive clearance between the high/low speed gear bushing and the output shaft; deformed shift fork or broken shift fork shaft positioning spring.

Solutions:

Adjust the clearance of each relevant linkage; replace damaged sliding sleeve and gears; replace gear bushings and adjust clearance; replace or repair the shift fork and replace the spring.

11. Increased hydraulic oil in the transmission, decreased hydraulic oil in the working hydraulic oil tank

Causes:

Aging oil seals in the working pump or steering pump; excessive axial or radial clearance of the working pump or steering pump shaft.

Solutions:

Replace the oil seals in the working pump or steering pump; repair and calibrate the oil pump. Or replace the oil pump.

12. Reduced hydraulic oil in the transmission, increased hydraulic oil in the working hydraulic oil tank.

Causes:

Clogged inlet filter in the working oil tank or clogged oil pump suction pipe.

Solutions:

Clean or replace the inlet filter; replace the oil pump suction pipe.

13. Low transmission pressure and weak machine movement after shifting into neutral or gear.

Causes:

Insufficient transmission fluid; clogged transmission oil pan filter; damaged or inefficient travel pump; improper pressure adjustment of the pressure reducing valve or inlet pressure valve; aged or severely bent travel pump suction pipe.

Solutions:

Add sufficient hydraulic oil to the transmission to the middle level at idle speed; replace or clean the filter; replace the travel pump; readjust the pressure to the specified range; replace the oil pipe.

14. The loader suddenly loses steering control while driving normally, although the steering wheel can be turned easily.

Fault Causes:

Steering cylinder piston detached

Steering column and steering gear connecting sleeve broken or damaged

Troubleshooting:

Replace the steering cylinder.

15. The loader suddenly loses steering control while driving normally, and the steering wheel cannot be turned.

Troubleshooting:

Steering pump keyway or connecting sleeve spline damaged.

Steering gear one-way valve detached (inside the valve block). Ф8Mn steel ball (one-way valve) inside the steering gear malfunctioning.

Replace the steering pump or connecting sleeve; replace the valve block or one-way valve.

16. Automatic steering; the steering wheel does not automatically return to the center position.

Fault Causes:

17. Steering wheel automatically deviates towards the concave side when encountering uneven ground.

Damaged two-way overload buffer valve.

Troubleshooting:

Replace the steering gear, clean and repair, or replace the valve block.

18. Heavy steering.

Fault Causes:

Clogged steering pump inlet filter or oil line; insufficient or no clearance at the steering column-to-steering gear connection; overly tight fit between steering gear valve core and sleeve, stator and rotor; low or stuck single-stable valve or overflow pressure adjustment; low steering pump volumetric efficiency.

Troubleshooting:

Clean the filter or replace the oil line; adjust its clearance; replace the steering gear or clean and grind it; adjust its pressure to the specified value; replace... Oil Pump

19. No Endpoint Steering Sensation

Causes:

Broken spring in the two-way buffer valve on the steering gear valve block, or the adjusted pressure of the two-way buffer valve is lower than the steering safety valve pressure; obstruction in the steering safety valve's fuel line; excessive clearance in the steering gear valve body, valve sleeve, valve core, or stator assembly due to severe wear.

Solutions:

Replace the spring or adjust its pressure to the specified value; clean and unclog the pipeline; replace the steering gear.

20. 50F Loader Suddenly Loses Lifting and Steering During Operation

Causes:

Broken pilot pump key or pilot pump shaft; damaged bearing at the connection between the torque converter and the pilot pump.

Solutions:

Replace the pilot pump or the keyway pin; replace the bearing.

21. Steering Wheel Turns but Steering Action is Slow; Steering Wheel Turns Lightly. Increased number of errors

Causes of failure:

Damaged steering cylinder piston seals

Damaged bidirectional overload buffer

Excessive wear clearance between rotor and stator, low steering pump efficiency

22. Abnormal noise from the front or rear axle when the loader turns, disappearing when driving straight

Causes of failure:

Mismatched or poorly meshed differential planetary gears and half-shaft gears, worn or damaged differential planetary gears, stuck planetary gears and differential cross shaft, or improper clearance adjustment

Solutions:

Replace the planetary gears or cross shaft gears, adjust the clearance, or replace the gears.

23. Noise from the loader's drive axle that persists even when coasting

Causes of failure:

Insufficient lubricating oil in the drive axle housing, excessively small meshing clearance between the driving and driven spiral bevel gears, or improper adjustment of the differential housing and... 24. **Excessive clearance in the planetary gear cross shaft:**

Troubleshooting:

Add sufficient lubricating oil according to standard, and adjust the clearance to the specified value.

**25.** Fault Symptom: Sudden loss of drive for both front and rear axles during operation.

**Cause:**

Broken half-shaft.

**Troubleshooting:**

Replace the half-shaft.

**26.** Loader is running normally, but abnormal noise is coming from all four wheels.

**Cause:**

Damaged tapered roller bearings on the wheel rims, damaged needle roller bearings on the planetary gear shafts, broken or damaged teeth on the sun gear and planetary gears, chipped teeth on the internal gear ring, broken bolts connecting the internal gear ring and its support frame.

**Troubleshooting:** Replace the bearings, adjust their clearance, replace the needle roller bearings, replace the sun gear and planetary gears, replace the internal gear ring, and replace the Ф10×75 bolts.

**27.** Sudden failure to lift, retract, or tip the bucket.

**Cause:**

The main safety valve of the work distribution valve is stuck.

**Troubleshooting:**

Open the main safety valve and clean it, paying special attention not to loosen the pressure adjusting nut at the rear of the safety valve. (Attached are images of the main safety valve location and its dissection)

Fault Analysis:

When the safety valve is stuck, all the hydraulic fluid from the working pump flows into the return oil circuit. The lifting cylinder and tipping cylinder oil circuits cannot build up the required working pressure, resulting in the boom and bucket not moving. This type of fault is generally caused by poor cleanliness of the hydraulic system. For machines that have been used for a long time, the hydraulic oil and suction filter should be thoroughly inspected or replaced.

27. Fault Phenomena:

1) Light load lifting speed is normal, but after exceeding a certain weight, it suddenly stops lifting or lifts extremely slowly. The fault symptoms are basically the same when the machine is cold or hot.

2) It can lift, but cannot reach the maximum lifting height.

Fault Causes:

1) Overload

2) The set pressure of the main safety valve in the work distribution valve is too low.

Troubleshooting:

1. Eliminate overload.

Overload can cause premature damage to the main safety valve and working pump!

2. Clean the main safety valve and recalibrate the pressure.

Note: The set pressure must meet the requirements of the instruction manual. Excessive set pressure may cause serious damage to the working pump, working valve, and high-pressure oil pipe!

28. The bucket tipping is normal, but the boom lifts slowly. The heavier the material being loaded, the slower the lifting speed. The problem worsens after the engine warms up.

Causes of the problem:

(1) Premature wear of the piston seals in the lifting cylinder. Diagnosis: Raise the boom to its highest position, disconnect the oil inlet connector of the piston rod chamber of one lifting cylinder, place the boom control lever of the work distribution valve in the "lift" position, and depress the high-speed throttle. Observe the leakage at the lifting cylinder interface. A slight leakage is normal. The same applies to the other lifting cylinder.

(2) Reduced efficiency of the working pump. After ruling out the first cause, it can be basically determined that the working pump efficiency is reduced.

Analysis:

The boom lifting speed is mainly determined by the working pump's speed, efficiency, and the leakage in the lifting oil circuit. 29. The boom stops at a certain position and does not stop, exhibiting a sinking phenomenon.

Causes:

Damaged seals on the lifting cylinder piston; excessive clearance between the working distributor valve stem and valve body.

Solutions:

Replace the piston seals; if the clearance between the valve stem and valve body is excessive, replace the working distributor valve.

30. During normal operation of the loader, the working hydraulic devices (lifting and tipping) suddenly stop working simultaneously.

Causes:

Damaged working oil pump; damaged splines and keyways on the working oil pump or broken drive pump shaft.

Solutions:

Replace the oil pump; replace damaged parts.

31. The working distributor valve (lifting linkage, boom linkage) control lever cannot be positioned.

Causes:

Damaged positioning sleeve. 31. The positioning steel ball is damaged, and the positioning spring is broken.

Troubleshooting:

Replace the positioning sleeve, replace the positioning steel ball, and replace the positioning spring.

32. When the loader is working, the bucket retracts weakly or automatically tilts down after retracting, and the bucket automatically retracts when encountering resistance at the bottom.

Causes:

Damaged seals in the bucket cylinder, stuck or damaged large-cavity overload valve, stuck or damaged small-cavity overload valve.

Troubleshooting:

Replace the seals on the piston, clean or replace the corresponding parts.

33. The loader produces noise in the working hydraulic system during both lifting and bucket retraction.

Causes:

Low hydraulic oil in the working oil tank, damaged or loose vacuum valve in the 30-type working hydraulic oil tank, old working oil tank suction pipe. Chemical suction cup flattening, loose oil pipe clamps on the working device, air intake in the oil pump suction pipe, malfunction of the main safety valve on the work distribution system.

Troubleshooting:

Add sufficient hydraulic oil to its standard value, tighten or replace the vacuum valve, clean the filter element or replace the oil pipe, clean and repair the main safety valve, and replace the main safety valve if necessary.

34. Oil leakage from the small hole at the rear of the positioning sleeve when operating the lifting or tipping valve stem.

Cause of failure:

Damaged O-ring on the valve stem and spring seat.

Troubleshooting:

Replace the O-ring and tighten it.

35. Low brake air pressure causing poor braking or no braking.

Cause of failure:

Damaged air compressor, air leakage in the pipeline, insufficient compressed air pressure, damaged or misadjusted multi-function unloading valve, low pressure.

Troubleshooting: Methods:

Inspect and replace damaged parts or the entire assembly; check and tighten leaks; loosen the unloading valve or adjust the pressure to its standard value.

36. Normal brake air pressure, but poor braking effect or no braking.

Causes:

Damaged brake chamber piston cup or air control shut-off valve; insufficient air venting from the brake valve; excessive wear on the brake drum and brake pads.

Solutions:

Replace the piston cup or air control shut-off valve; adjust their clearance or replace the brake valve; replace damaged parts.

37. Abnormal noise during braking.

Causes:

Brake shoe friction pads are too hard or rivets are exposed; metal shavings are trapped between the brake drum and friction pads; overheating of the brake causes the friction pad surface to harden.

Solutions:

Eliminate the above phenomena.

38. The brakes veer to one side during braking.

Possible causes:

Uneven clearance between the front brake discs and friction pads; uneven contact area between the front brake pads; air in one front brake piston; deformed front brake caliper; inconsistent air pressure in the two front wheels; oil or dirty water on one side brake pad.

Solutions:

Inspect the brake discs and friction pads; replace if damaged. Inspect and replace the friction pads. Bleed the air correctly and replace them. Ensure the air chamber is at the specified pressure and the pressure is consistent. Clean and dry the chamber.

39. Brakes suddenly fail when the brake pedal is fully depressed while driving.

Possible causes:

Damaged or overturned master cylinder seal; no brake fluid in the master cylinder; no brake pressure; severely ruptured brake lines or disconnected pipe joints.

Solutions:

Replace damaged seals; add sufficient brake fluid to the standard value; bleed the air from the hydraulic system; replace damaged brake lines.

40. Brake discs sag during continuous driving.