First, the maintenance tools of automobile automatic transmission
There are many tools used to maintain the automatic transmission of automobiles, which can be roughly divided into the following categories:
① Common tools: Allen wrench, external hexagon wrench, socket and torque wrench, pliers, chisel and file.
Tools, taps and dies, etc.
② Special tools: bearings, bushings, special gear puller, positioning ring pliers, etc.
③ Power tools: pneumatic or electric wrenches, ratchets, etc.
④ Lifting tools: jacks, safety supports, hydraulic or electric lifts, etc.
⑤ Measuring tools: internal micrometer, external micrometer, dial indicator, feeler gauge, etc.
⑥ Test instruments: multimeter, oscilloscope, monitor, flaw detector, etc.
Second, the routine inspection items of automobile automatic transmission
Routine inspection items of automobile automatic transmission include: automatic transmission oil level inspection, oil quality inspection, automatic transmission oil leakage inspection, engine throttle opening inspection, gear lever inspection, automatic transmission control switch operation inspection, engine idling inspection, etc.
Three, the general maintenance procedure of automobile automatic transmission fault
Fault diagnosis and detection procedures: preliminary inspection → fault code inspection → manual shift test → mechanical system test → hydraulic system test → electronic control system test → inspection of common faults, cause analysis and troubleshooting methods.
(1) Confirm the fault phenomenon according to the fault phenomenon analysis.
(2) If it is an electronically controlled automatic transmission and the fault indicator light is on, self-diagnose first, read the fault code, and eliminate the fault represented by the fault code.
③ Routine inspection of automatic transmission and engine. The main projects are:
A. check the oil level and oil quality.
B check and adjust the accelerator pedal cable and the accelerator position sensor.
C. check the linkage system of the selector lever handle.
D. check the neutral start switch and gear switch.
E. check the engine idle speed.
F check the tire pressure and other related parts of the transmission system.
④ Carry out stall test to check the internal mechanical and technical conditions of the engine and automatic transmission.
⑤ Manual shift test; Determine whether the fault is in the electronic control part or inside the automatic transmission.
⑥ Conduct time lag test to check the wear of clutch and brake of daily transmission.
⑦ Self-diagnosis of electronic control system and detection of components and circuits.
Today oil pressure test, check the oil pump, pressure regulating valve, governor oil pressure and oil pressure.
Pet-name ruby road test, check the automatic shift point, with or without abnormal noise, vibration, slip and start.
The braking function of the machine, etc.
Attending comprehensive test results, analyze and judge the cause and location of the fault.
Four, automatic transmission maintenance matters needing attention
① The fault of automatic transmission is related to engine, electronic control system and automatic transmission, and it should be confirmed that the fault is inside the automatic transmission before disassembly and maintenance.
(2) To lift or support the vehicle, if it is only necessary to jack up the front or rear end of the vehicle, the wheels must be plugged with triangular wood.
(3) When removing and checking electrical components, the negative connection of the battery should be removed first. After the negative connection of the battery is removed, the audio system and the anti-theft system may be locked, and some system setting parameters may disappear, so relevant records must be made before power failure.
(4) When replacing the fuse, the new fuse must have a considerable current intensity, and the fuse that exceeds or falls below the specified current value cannot be used; Check the electrical components with a digital multimeter with an appropriate range to avoid damaging the parts.
⑤ Before disassembling the automatic transmission, thoroughly clean its exterior to prevent dust from polluting internal parts. Because even small sundries may cause the hydraulic system of automatic transmission to malfunction.
⑥ When disassembling the automatic transmission, all parts should be put away for reassembly. Especially when disassembling the valve body assembly, the valve should be put together with the spring.
⑦ Thoroughly clean all parts of the decomposed automatic transmission, and blow all oil passages and oil holes with compressed air to ensure no blockage. It is recommended to clean parts with automatic transmission oil or kerosene. After cleaning, blow dry with air.
⑧ Before assembly, carefully check all parts and components, and replace them if they are damaged. Ruo component
Pet-name ruby disposable parts cannot be reused, such as cotter pins and seals.
Attending the bushing needs to be replaced due to wear, and the support must be replaced together.
⑾ Needle roller bearing and raceway are worn or damaged and should be replaced.
⑿ When replacing new clutch and brake friction plates, they must be soaked in automatic transmission oil for at least 65438 05 minutes before assembly.
[13] Before assembly, all sealing rings, rotating parts and sliding surfaces should be coated with automatic transmission oil.
14. You can use grease (butter) to stick small parts in the corresponding positions for assembly.
⒂ The position and installation direction of all needle roller bearings and raceways should be correct.
[14] Do not use sealant on gaskets or similar parts.
⒄ All parts and components shall be assembled in the reverse order of disassembly; Tighten the screws according to the specified torque.
In all disassembly and assembly processes, special tools should be used as much as possible.
Trick: Check the hose and wire terminal to ensure the correct and reliable connection.
Five, maintenance skills
◆ Troubleshooting of shift impact of automatic transmission
(1) fault phenomenon
At the beginning, when the shift lever is shifted from P or N to D or R, the car vibrates greatly. When driving, the automatic transmission vibrates instantly when upshifting.
(2) Cause of failure
Engine idle speed is too high; Improper adjustment of throttle cable or throttle position sensor leads to high oil pressure in the main oil circuit; Upshift is too late; The vacuum hose of vacuum throttle valve is damaged; The pressure regulating valve of the main oil circuit is faulty, which makes the oil pressure of the main oil circuit too high; The piston of the shock absorber is stuck, and there is no vibration reduction effect; The check valve ball is missing, and the brake or clutch is engaged too fast; The shift assembly slips; Oil pressure solenoid valve failure; Electronic control unit failure.
(3) Exclusion method
Check the engine idle speed; Check and adjust the throttle cable and throttle position sensor; Check the vacuum hose of the vacuum throttle. Road test to check whether the automatic transmission upshift is too late, which is a common reason for the large shift impact.
Check the oil pressure in the main oil circuit. If the oil pressure in the main oil circuit is high when idling, it means that the pressure regulating valve or throttle valve in the main oil circuit is faulty; If the idle oil pressure is normal and the starting impact is large, it means that the air inlet check valves of the forward clutch, reverse clutch and high-grade clutch are damaged or missing.
Check the oil pressure in the main oil circuit when shifting gears. Under normal circumstances, the oil pressure in the main oil circuit should drop instantly when shifting gears. If it does not descend, it means that the damper piston is stuck, and the valve body and damper should be disassembled for inspection.
Check whether the oil pressure solenoid valve works normally; Check whether the electronic control unit sends a control signal to the oil pressure solenoid valve during gear shifting. If there is something wrong with the solenoid valve itself, it should be replaced; If there is something wrong with the wiring, it should be repaired.
◆ Troubleshooting of Automatic Transmission Slipping Fault
(1) fault phenomenon
When stepping on the accelerator pedal at the beginning, the engine speed rises quickly but the vehicle speed rises slowly; It was very weak when going uphill, and the engine speed rose very high.
(2) Cause of failure
Hydraulic oil level is too low; The clutch or brake is badly worn; The oil pump is seriously worn, and the oil pressure in the main oil circuit is low due to oil leakage; One-way overrunning clutch slips; Damage of clutch or brake sealing ring leads to oil leakage; Damage of piston sealing ring of shock absorber leads to oil leakage.
(3) Exclusion method
Check the oil level and quality of hydraulic oil; If the hydraulic oil changes color or smells burnt, it means that the friction plate of the clutch or brake is burnt out, and the automatic transmission should be disassembled for inspection.
The road test shows that if all gears slip, the reason is the forward clutch.
If the selector lever slips in the second gear of the D gear, but does not slip in the second gear of the S gear, it means that the one-way overrunning clutch of the second gear slips. If it is the second gear slip in D position and S position, it is the low gear and reverse gear brake slip. If you slip in the third gear, the reason is that the reverse gear and the high-grade clutch are out of order. If you slip in overdrive, it's an overspeed brake failure. If you slip in reverse and high gear, it is a clutch failure in reverse and high gear. If it slips in reverse gear and 1 gear, it is a low-speed reverse brake slip.
Slipping in both forward and reverse indicates that the oil pressure in the main oil circuit is low. At this time, the oil pump and valve body should be overhauled. If the oil pressure in the main oil circuit is normal, the reason may be that the friction plate of the clutch or brake is excessively worn or burnt, so just replace the friction plate.
◆ Troubleshooting of Automatic Transmission Failure to Upshift
(1) fault phenomenon
When driving, the automatic gear can only be upshifted to 1 gear, and cannot be upshifted to 2nd gear and high gear; Or you can move up to second gear, but you can't move up to third gear or overspeed gear.
(2) Cause of failure
Improper adjustment of throttle cable or throttle position sensor; The governor is faulty; Governor leaks oil; Vehicle speed sensor failure; The second brake or high-grade clutch is faulty; The shift valve is stuck or the gear switch is faulty.
(3) Exclusion method
Fault diagnosis should be carried out first for electronically controlled automatic transmission. Check and adjust the throttle cable and throttle position sensor; Check the speed sensor; Check the gear switch signal. Measure the oil pressure of the governor. If the oil pressure of the governor is 0 or very low after the speed increases, it means that the governor is faulty or leaks oil. If there is no fault in the control system, disassemble the automatic transmission to check whether the shift actuator assembly slips, whether the clutches, brake cylinders or pistons leak, and whether there is compressed air.
◆ Troubleshooting of slow upshift of automatic transmission
(1) fault phenomenon
When the car is running, the upshift speed is high and the engine speed is also high; Before upshifting, the accelerator pedal must be released to upshift the automatic transmission.
(2) Cause of failure
Improper adjustment of throttle cable or throttle position sensor; The governor is faulty; The sealing ring of the oil inlet and outlet hole of the governor on the output shaft is damaged; Improper adjustment of push rod of vacuum throttle valve; The vacuum hose or vacuum diaphragm of the vacuum throttle valve leaks air; High oil pressure in the main oil circuit or throttle valve; Forced downshift switch is short-circuited; Sensor failure.
(3) Exclusion method
Fault diagnosis should be carried out for electronically controlled automatic transmission. Check and adjust the throttle cable or throttle position sensor, measure the resistance of the throttle position sensor, and replace it if it does not meet the standard. For automatic transmission with vacuum throttle, check the vacuum hose for leakage. Check the forced downshift switch for short circuit.
Measure the oil pressure of the idle main oil circuit. If the oil pressure is too high, it should be adjusted by throttle cable or throttle position sensor. Automatic transmission with vacuum throttle should be adjusted by reducing the length of throttle push rod. If the above adjustment fails, remove and check the oil pressure valve or throttle valve.
Measure the oil pressure of the governor. The oil pressure should increase with the increase of vehicle speed. Compare the governor oil pressure measured at different speeds with the specified value. If the oil pressure is too low, it indicates that the governor is faulty or the oil circuit of the governor is leaking. At this time, the automatic transmission should be disassembled for inspection to check whether the governor fixing screw is loose, whether the governor oil circuit sealing ring is damaged, and whether the valve core is stuck or excessively worn.
If the oil pressure of the governor is normal, the reason for the slow upshift may be that the shift valve is not working properly. The valve body should be disassembled for inspection and replaced if necessary.
◆ Troubleshooting of automatic transmission without forward gear
(1) fault phenomenon
Reverse gear is normal, but it can't drive in D gear; The car can't start in D gear, but it can start in S gear and L gear (or 2, 1 gear).
(2) Cause of failure
The forward clutch slips; The forward one-way overrunning clutch slips; The forward clutch leaks oil; Improper adjustment of gear selection handle.
(3) Exclusion method
Check and adjust the position of the gear selection handle. Measure the oil pressure of the forward main oil circuit. If the oil pressure is too low (indicating that the oil pressure in the main oil circuit is low), disassemble and inspect the automatic transmission and replace the sealing ring on the forward oil circuit. Check the forward clutch. If the friction plate is burnt or excessively worn, replace it. If the oil pressure in the main oil circuit and the forward clutch is normal, disassemble and check the forward one-way overrunning clutch.
◆ Troubleshooting of Automatic Transmission without Overdrive
(1) fault phenomenon
When the car is driving, you can't change from the third gear to the overspeed gear; The vehicle speed has reached the working range of overdrive, and the automatic transmission cannot be upgraded to overdrive by releasing the accelerator pedal for a few seconds and then stepping on the accelerator pedal.
(2) Cause of failure
Overspeed switch failure; Overspeed solenoid valve failure; Overspeed braking skidding; The direct clutch or direct one-way overrunning clutch on the overspeed planetary gear fails; Gear switch failure; Hydraulic oil temperature sensor failure; Throttle position sensor failure; The 3-4 shift valve is stuck.
(3) Exclusion method
Fault diagnosis should be carried out on the automatic transmission of the electronic control system to check whether there is a fault code output.
Check the resistance value of the hydraulic oil temperature sensor; Check the output signals of gear switch and throttle position sensor. Gear switch, the signal should be consistent with the position of the selector lever handle, and the output voltage of the throttle position sensor should be proportional to the throttle opening.
Check the overspeed switch. When in the on position, the contact of the overdrive switch should be disconnected, and the indicator light will not light up; In the off position, the contact of the overdrive switch should be closed and the indicator light should be lit. Otherwise, check the overdrive circuit or replace the overdrive switch.
Check the operation of the overdrive solenoid valve. Turn on the ignition switch, do not start the engine, press the O/D switch, and engage the overdrive solenoid valve. If there is no engagement sound, check the control circuit or replace the solenoid valve.
Lift the vehicle with a hoist so that the four wheels are suspended. Start the engine, let the automatic transmission work in D gear, and check the upshift of the automatic transmission under no-load condition. If you can shift to the overdrive gear and the vehicle speed is normal, the control system works normally. If you can't shift into overdrive, it's because the overspeed brake slips, so you can't shift into overdrive with a load. If you can upshift into overdrive gear, but the speed is not high and the engine speed decreases after upshift, it means that the direct clutch or the direct one-way overrunning clutch in the overspeed planetary row is faulty. If you can't shift into overdrive when there is no load, it means that the control system is faulty, so you should remove the valve body and check the 3 ~ 4 gear shift valve.
◆ Troubleshooting of automatic transmission without reverse gear
(1) fault phenomenon
This car can drive in D gear, but not in reverse gear.
(2) Cause of failure
Improper adjustment of gear selection handle; Reverse oil leakage; Reverse and high clutch or low and reverse brake slip.
(3) Exclusion method
Check and adjust the position of the shift lever handle. Check the oil pressure in the reverse oil circuit. If the oil pressure is too low, it means that the reverse oil circuit is leaking, and the automatic transmission should be removed for inspection.
If the oil pressure in the reverse oil circuit is normal, remove the automatic transmission and replace the damaged clutch or brake friction plate or brake band.
◆ Troubleshooting of frequent gear jumps of automatic transmission
(1) fault phenomenon
When the car is driving, the automatic transmission suddenly downshifts, and after the downshift, the engine speed increases, resulting in shift impact.
(2) Cause of failure
Throttle position sensor failure; Vehicle speed sensor failure; Control system circuit failure; Poor contact of shift solenoid valve; Electronic control unit failure.
(3) Exclusion method
Fault diagnosis of electronically controlled automatic transmission.
A sensor for measuring the throttle position; A sensor for measuring vehicle speed.
Remove the automatic transmission oil pan and check the terminal of the solenoid valve connecting wire; Check the voltage of each terminal of the control system.
◆ Troubleshooting of engine without braking
(1) fault phenomenon
When the car is driving, when the shift lever is in the 2/1 or S/L position, release the accelerator pedal, and the engine speed will drop to the idle speed, but the car will not obviously slow down. When going downhill, the automatic transmission is in the forward low gear, but it cannot produce engine braking effect.
(2) Cause of failure
Improper position adjustment of gear selection handle; Improper adjustment of gear switch; Forced braking skids in 2nd gear or skids in low gear and reverse gear; The solenoid valve for controlling engine braking is faulty; Valve body failure; Automatic transmission failure.
(3) Exclusion method
Fault diagnosis of electronically controlled automatic transmission.
Test drive to check whether the automatic transmission slips.
If the selector lever handle has no engine braking function when it is in the S position, but it has engine braking function when it is in the L position, it means that the second gear is forced to brake and slip. If the shift lever has no engine braking function when it is in the L position, but it has engine braking function when it is in the S position, it means that the low and reverse brakes are slipping.
Check the solenoid valve that controls the engine braking function for faults. Remove the valve body and clean all control valves. Check the voltage of each terminal of the electronic control unit. If it is normal, check the voltage of each sensor. Replace the electronic control unit with a new one and try again. If the fault disappears, the electronic control unit is damaged.
◆ Troubleshooting of Lockless Clutch of Hydraulic Torque Converter
(1) fault phenomenon
When the car is driving, the speed and gear have met the clutch locking conditions, but the locking clutch still has no locking effect; Fuel consumption has increased.
(2) Cause of failure
Locking solenoid valve failure; Locking control valve failure; The lockup clutch in the torque converter is damaged.
(3) Exclusion method
Check the locking solenoid valve; Check and clean the locking control valve; If there is no fault in the control system, replace the torque converter.
◆ Troubleshooting of Forced Downshift Failure
(1) fault phenomenon
When the car is driving in the third gear or overspeed gear, the accelerator pedal is suddenly stepped to the bottom, and the automatic transmission can't immediately downshift by one gear, so the car can't accelerate.
(2) Cause of failure
Improper adjustment of throttle cable or throttle position sensor; Forced downshift switch is damaged; Forced downshift solenoid valve short circuit or open circuit; The forced downshift valve is stuck.
(3) Exclusion method
Check the installation of throttle cable and throttle position sensor.
Check the forced downshift switch. When the accelerator pedal is pressed to the bottom, the contact of the forced downshift switch should be closed; When the accelerator pedal is released, the contact of the forced downshift switch should be disconnected. If the accelerator pedal is pressed to the bottom, the forced downshift switch will be triggered.