6 Transmission & Steering Hydraulics SD22 & SD32 Hydraulic System:Transmission and steering control systems are separated to each other, they draw oil from different pumps, but all the oil is from steering clutch case. The oil flows to the torque converter after transmission and steering, then the oil flows back to steering clutch case.So, the transmission and steering are one system called transmission & steering hydraulic system.
8 Transmission & Steering Hydraulic System SD16 Hydraulic System:Transmission and Steering control systems draw oil from Transmission case and Steering clutch Case. Oil flows to torque converter after transmission, then to transmission pan again through oil cooler. However steering clutch oil flows back to steering clutch case.So, the transmission and steering are two different systems.
12 Assembly & Operation Gear Pump: Bulldozer Transmission & Steering Pumps are high pressure gear pumps. Their construction is simple and very efficient.Transmission Valve:SD22, SD32 have the same transmission valve unit. It is consists of Relief Valve, Return Valve, Pressure Reduction Valve, Speed Control Valve, Safety Valve and Direction Valve.Relief Valve & Return Valve are for transmission oil pressure, Speed Control Valve is for shift change, Direction Valve is for Forward and Reverse, Pressure Reduction Valve is for First Shift, Safety Valve is for protection of starting machine.
16 Modulating Relief Valve: The modulating relief valve controls the buildup of oil pressure when the gear shift lever is operated and the clutch engaged, so as to avoid shock during start and off and improves the service life of power shift transmission.Modulating Time
17 Steering ValveSD32, SD23, SD22 and SD16 steering valves’ structure and principle are the same.Steering & brake hydraulic system includes relief valve, steering control valve, brake booster valve.they have a bypass/relief valve, to avoid abnormal oil pressure if the filter is clogged.
22 Chapter Three Troubleshooting & Problem Solving
23 Methods of Troubleshooting Hydraulic system problems are caused by many factors.The Process of identifying a problem:Watch →Test Machine →Check PressureResolving the problem:a. Refer to Operation or Shop Manualb. Carry out adjustments/fit replacement parts
25 1. Gearshift inoperative Reason:a. Inner Transmission Box:1. the gearshift’s cylinder seal damagedor installed wrong2. Oil path leak3. if First Shift is inoperative:1) Ball of anti return valve is broken2) Oil path rotating seal ring is damagedb. Hydraulic system:1. the 5 O-rings of clutch oil entrance in the seat oftransmission valve are damaged2. the factors of the pressure reduction valve:If the pressure reduction valve is blocked at closed position, 1st gearshift is inoperative; if the pressure reduction valve piston hole is blocked, the oil pressure will increase, leading to worn seals, the 1st gearshift is inoperative.
26 2. The machine drives on Neutral Gearshift Reason:Incorrect adjustment of the direction valve positionForward and reverse clutch disc distorted or broken, it locked, the clutch can’t separate completely.
27 3. The machine will not drive Reason:The machine will not drive on any gearshift position, it’s because the clutch can’t get oil.Transmission pump damaged, it can’t draw oil.Transmission pump seal leak.Transmission case oil level is down.Oil piping leak, problem with pump.Relief valve is blocked, 5 clutches have no oil pressure.
28 4. Gearshift LagReason:the clutch can’t get oil, suction piping leak.Relief valve’s relief spring is broken, it delays the pressure increase in time.
29 5. Hot machine no drive, but cold machine is normal. Reason:The suction pipe is aging or worn or distorted, and the suction ability is not good.The oil is thin, clutch can’t engage properly, so the hot machine has low power.
30 6. Transmission Torque Reduced Reason:Relief valves blocked, the valve can’t move correctly, the oil pressure is low and the clutch can’t engage.
31 7. Torque converter over heating Reason:Torque converter problem:1. return oil pump filter is blocked2. the seal leakingHydraulic system problem:1. oil quality is not good2. oil quantity is low, or oil leak3. insufficient cooling.
32 8. Steering filter cover bulged Reason:Relief valves blocked or inlet blocked, the high pressure bulges the cover. Must clean the relief valve.
33 9. Poor Steering Control Reason: Pulling the steering lever to the end and the pressure normal, the reason is that steering lever is adjusted incorrectly.
34 10. One side no steering, another side is normal Reason:“S” tube o-ring is damagedClutch intake oil rotation seal is damagedClutch piston seal is damaged
35 Reason: 11. Cold machine has steering, but hot machine has not steeringReason:The tube between steering pump and filter is damaged, so oil can’t pass through.The oil becomes thin as the machine warms up, or the seal is worn, oil leak, oil pressure decrease.
36 12. Pulling one steering lever, the machine will stop Reason:This phenomenon shows that another side can’t transfer power, maybe another side steering direction valve block at open position.
37 13. Sometimes steering is intermittent Reason:Steering suction oil system seal is damaged and steering pump can’t get enough oil, the pressure is down.Due to steering pump drawing air, the oil filter has not oil, it leads transmission pump to draw air too. So sometimes transmission failure is caused by steering system damage.When the pump draws air, there are sharp whistle, and there are many air bubbles in oil.
38 14. Braking is poor Reason: Brake band is worn out, need adjustment or replacementBrake linkage are adjusted incorrectlyBrake booster valve don’t seal well
39 15. Pushing force is poor Reason: Engine Torque Converter Transmission Steering Clutch
40 15. Pushing force is poor Check for the position of problem: If the universal joint rotates, the malfunction is after engine or torque converter.If the universal joint does not rotate, then the malfunction is before transmission or steering clutch.If bevel gear rotates, the problem is at steering clutch; if bevel gear does not rotate, the problem is at transmission.
41 15. Pushing force is poorCheck for the Pressure:If the pressure is right, it must be that there is mechanical malfunction or inner failure.If the pressure isn’t normal, we must diagnose, by referring to the manual.
43 to Diagnose hydraulic problems Pressure Measurementto Diagnose hydraulic problems1. Important Measurementsa. Oil brand, quality and grade are correct, steering case oil level correctb. Warm-up engine, ensure coolant and oil temperature are in 70-90oCc. Engine is at operating speed2. Measurement MethodMeasure the oil pressure at engine full speed and idle speed.3. Measure Points, Standard Pressure (theoretic data in manual)
45 Machine will not move on selecting a gear Measure relief valve pressure: low is 0.1, full speed is 0.3MPa.Due to this low pressure, gear clutch can’t get enough force, the machine can’t move.Discharge the air in steering filter, the pressure raised, but once engine stops 10 minutes later start again, the pressure is low again. This means that air is in the pump, replace the O-ring, and the problem is solved.
46 2. Speed is low in any gearMeasure transmission relief valve pressure: low is 0.4MPa, full speed is 0.7MPaDue to this low pressure, discharge the air from filter, it is not helpful.Then check the return valve, then find the valve piston is blocked, the oil is leaking from output. Clean the valve piston, reset it again, the problem is solved.
47 3. Power is down on the mid rpm Measure transmission relief valve pressure: low is 1.0MPa, full speed is 3.5MPa, the pressure changed too much with increased engine speed, it means that the relief valve need to be adjusted.After checking, finding the valve piston is blocked with many carbon and corrupted hollows. After cleaning valve piston, reset it again, the problem is solved.
48 4. Torque converter power decrease Measure transmission and steering relief valve pressure: both are normal.Measure the entrance of torque converter, the oil pressure is 0.4MPaCheck torque converter safety valve, if spring is broken, replace it, the problem is solved.
49 5. If hydraulic oil temperature high, long term working, then the valve will block easily Measure transmission valve, the pressure is normal.Measure the entrance of torque converter, low speed pressure is 0.1MPa, full speed oil pressure is 0.5MPa.Due to the entrance pressure being low, the oil flow is low and cooling poor, so the temperature is high.Check torque converter, check the seal of inner oil path for damage, replace it, the problem is solved.
50 6. No steering at low speed, but at increased engine rpm, the steering is ok. Measure steering relief valve pressure: low speed pressure is 0.4MPa, full speed oil pressure is 1.1MPa;And steering clutch oil pressure is low.At the same time the valve is faulty.It means that steering relief valve is the problem, check it, if the spring is broken, replace it, the problem is solved.
51 7. Cold machine steering is normal, but after working, the steering is very heavy Measure steering relief valve pressure: low speed oil pressure is 0.5MPa, full speed oil pressure is 1.1MPa;Steering relief valve oil pressure is low, it is caused by a blockage of relief valve.Disassemble and clean it, the problem is solved.
52 8. One side steering is not serviceable Steering relief valve pressure is normal, other side steering brake pressure is normal too, but this side steering brake pressure is low.It show this booster or its piping has a leak.Disassemble booster, check the piping entrance o-ring is damaged, replaced it, the problem is solved.
53 The End of This Training Module Thanks Your Cooperation !!!