A 1998 European-style Toyota Land Cruiser 4700 off-road vehicles, equipped with A442F 4-block electronic control automatic transmission, the car in the normal operating temperature of the engine, the standard idling conditions, the shift lever P → D and N → D when the transmission The impact of serious, other conditions are good (including the reverse gear and forward gear up and down control).
The Toyota A442F Automatic Transmission is a fully electromechanical transmission with a 2-speed splitter device consisting of a torque converter with an electronic locking function, a high efficiency gear pump with four Solenoid valve hydraulic control valve body assembly, and internal mechanical components. The internal mechanical components include: forward clutch, direct gear / reverse clutch, overspeed clutch, 2 block brake, overspeed brake, low / reverse brake, 3 sets of planetary gears and two one-way clutch.
For the Toyota car transmission into the D block impact of the fault, the main reasons for the failure of the following.
① throttle pull line adjustment improper.
② D bit main oil pressure is too high.
③ D-bit main actuator The accelerator of the forward clutch Clutch C1 can not perform buffer control.
④ advance the clutch C1 itself.
⑤ The N-D buffer control of the electronic control unit is disabled.
According to the above ideas, first check the adjustment of the throttle pull line position, and through the necessary means to check the transmission external electronic control (electronic unit N-D buffer control) is normal. After checking and adjusting the throttle line, it measures the main oil pressure at the D position of the transmission shift lever. As a result, the oil pressure value is basically within the standard range, and it can change with the change of the throttle opening. The possibility of hydraulic control valve body problems is not great. In order not to expand the scope of maintenance, decided to first check and clean the transmission hydraulic control valve body. But the cleaning body after loading test, the phenomenon did not significantly change, had to further check the other parts.
Due to the structural design of the A442F, it is necessary to disassemble the splitter when breaking down the accumulator of the forward clutch Clutch C1. After inspection, no signs of wear and jam in the accumulator piston and cylinder were found. So the use of compressed air again test the operation of the accumulator, the results of the piston movement is very flexible, no abnormal phenomenon. As a result of the above check did not find the problem, only the decomposition of automatic transmission assembly to check. After disassembling the transmission, it is decided to check the relevant components inside the transmission. When the forward clutch Clutch C1 in the transmission was inspected, the working gap was found to be 3.8 mm, which was far beyond the limit of 1.7 mm in the maintenance manual, and the buffer disc of the clutch itself had lost its cushioning effect. It is important to note that the transmission has been repaired several times (there is a problem with some local assembly).
Finally, in accordance with the routine maintenance procedures to replace all the sealing components, replace the forward clutch Clutch C1 buffer control disc, and C1 clutch clearance adjusted to the specified value of 1.7mm, the transmission installed test, troubleshooting.
Summary: Regardless of the maintenance of the form of automatic transmission failure, must have a clear diagnosis of ideas, and to master the correct steps.