get the thing level up in the air very safely, make sure the car isnt gonna fall off if you have stands....
get the correct hex to remove the filler from underneath... trans should be warm to the touch as you hold your hand on the trans pan, if its comfy its not hot enough, if its hardly bearable its the right temperature to unbolt the filler to check.
Make sure you have the car idling, run with the brake on through all the gears and then put it back in park. Then go under and check/fill...it's a chore but with no leaks its good till the next 30k filter change.
95 E34 530I V2.37
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Those who make peaceful revolution impossible will make violent revolution inevitable.
John F. Kennedy