Problem Automatic transmission

Hello guys, I've had an Audi S6 4.2L V8 Avant Bj.12.1995 for 2 months now, with automatic transmission.

but now have 2 problems with the Autom transmission.

on the one hand, the gearbox switches back and forth, with different driving modes. What can that be? or even at higher rotational...
And on the other hand, since today I am losing the axle differential oil, how much game can I have in the flange where the drive shaft is screwed on? (i.e., the front axle) I can use this flange so approximately. May pull 3-5mm out, and also have height play in it???

would be great if someone could help me further


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