What size socket would one use on the drain plug of the front differential of a 2000 A/T Legacy. Its larger than 13/16 and 17mm, 20mm perhaps?

Does it have a squre hole in the middle like the older subarus? Then use a 1/2" drive ratchet, no socket.

the hole in the middle seems round not squared like the rear

From memory it is 19mm

its 13/16 if anyone needs to know

drag your tool set under the car w/ you, and try each one... usually how i work

found like some sort of metallic sludge on the magnets that are on the inner side of the drain plugs, must be the gears grind up everything metallic that gets shaved off and then it transforms into sludge that is picked up by the magnets, interesting.

I wouldn't worry about a little sludge, but metal shavings would be a big opps!