The stall speed of Toyota Land Patrol gearbox is slow.

① Improper adjustment of throttle cable.

② The oil pressure in the main oil circuit at position D is too high.

③ The accumulator of the forward clutch C 1 and the main actuator at position D cannot be buffered.

④ The problem of the forward clutch C 1 itself.

⑤ The N-D buffer control of the electronic control unit is invalid.

According to the above ideas, firstly, check and adjust the position of the throttle cable, and check whether the electronic control (electronic unit N-D buffer control) around the transmission is normal by necessary means. After checking and adjusting the throttle cable, measure the main oil pressure of the shift lever of D-gear transmission. The results show that the oil pressure value is basically within the standard range and can change with the change of throttle opening. This shows that the hydraulic control valve body is unlikely to have problems. In order not to expand the scope of maintenance, it is decided to check and clean the hydraulic control valve body of the transmission first. However, the valve body was put into trial operation after cleaning, and the fault phenomenon did not improve obviously, so we had to further check other parts.