The buzzing sound is the oil pressure regulator solenoid valve. The sound is normal and also the reason why they fail...they do a lot of work. There is no pressure regulating in neutral or park.
I agree with everyone else, if you have no oil pressure and you have no drive, then it must have something to do with the oil pump. Either directly or indirectly (pump or torque converter).
The outer shell of the torque converter transmits power from the engine to the oil pump...constantly, while the engine is running. I do not know how the torque converter is coupled to the pump (in the AL4) so I can not comment on a failure mode.
Here is some propaganda on the AL4 on youtube. Unfortunately it's in french (of course)
As stated, it could be a lot of things but, logically, you would start with some condition that you could have "altered" with your maintenance.
I agree with everyone else, if you have no oil pressure and you have no drive, then it must have something to do with the oil pump. Either directly or indirectly (pump or torque converter).
The outer shell of the torque converter transmits power from the engine to the oil pump...constantly, while the engine is running. I do not know how the torque converter is coupled to the pump (in the AL4) so I can not comment on a failure mode.
Here is some propaganda on the AL4 on youtube. Unfortunately it's in french (of course)