How to troubleshoot the gearbox on BMW 5 Series?

BMW 5 Series indicates that the gearbox is faulty, because the internal gear oil is too dirty, resulting in abnormal operation of the gearbox solenoid valve. It can be recovered by changing the gear oil of BMW 5 Series gearbox. The specific operation steps are as follows:

1. Remove the oil drain screw of the gearbox.

2. Drain the gearbox oil.

3. Remove the gear box bottom shell.

4. Install a new gearbox chassis.

5. Add gearbox oil and it's done.