liquid for automatic transmission Malibu 1971

[Tonioh]

Hello to you all,
I have in my ownership Chevrolet Malibu on 1971.
There is a light leak after use of the vehicle.
I verified the oil of the engine and it is not that.
Furthermore, recently there is a strong noise which is listened as a grating under my feet when I am in free wheel (before braking and before an acceleration). I think in particular of the propeller shaft.
I deduct that from it the leak comes probably from the reservoir of the liquid of the automatic transmission But I do not know which product to put in it and I do not know where is the pull of this reservoir.