What size (allen) hex head socket to remove axle?

17mm

no size will fit
 

(properly) because it is not an allen/hex type. They are triple-squares / 12-point.

I believe it is a 10mm for the B5S4 (and 8mm for the B5A4)

<img src="http://ctny.audiworld.com/mark/s4/clutch/4_remove/dsc01970.jpg">

ohhhhh, *that* bolt ;-)

you're referring to the bolts that hold the inner cv to the tranny. They're 10mm triple squares
 

NAPA, Autozone and a few other places carry them

Dave

which need to be removed to remove those "axles"....
 

EDIT: I had thought I had removed my half shafts entirely and was thinking I didn't remove that big bolt - but I only removed the inner CV connections.

Bolt holding axle to hub?
 

Thanks for all the replies. I guess I wasn't clear enough but thanks.

which axle?

FYI, the center shaft uses standard allens...
 

<img src="http://ctny.audiworld.com/mark/s4/clutch/4_remove/dsc01965.jpg">

huh? you're losing me. The front axle DOES have a 17mm driveshaft bolt that secures the splines of
 

the driveshaft the the hub / spindle assembly. The other half of the axle is connected to the transmission by the 10mm triple squares.

Dave