Filler Plug On Differential Won't Come Off

I was going to check the gear oil in my rear differential but the plug was messed up so bad I couldn't get it off. Apparently, the previous owner managed to round off the plug to the point where the 3/8 driver will just twist around the inside. Vice grips won't work either because the plug is almost flush with the surface.
Anybody have any suggestions how I can get this plug off? I have a new one to replace it with, if I can ever get it off.

Thanks, Jeff

weld a 3/8 driver in? Super glue?

you may have to remove the whole cover on the back of the differential. Its messy so be sure to have a big pan to catch the gear oil, then you can work on removing the plug right in front of you. Just be sure you buy a new seal before you put the cover back on.
good luck

I have found that a T55 works great for this T-55 is a torx bit or star head as some would call it beat it in once its in you should be able to loosen it with a ratchet

They sell roundoffs or something like that at sears. They are spiral cut sockets so they will chew the rest of the bolt up but it should be enough to get the bolt out. I screwed up some bolts on the rear of another car using an imact whrench which was tightening when I thought it was loosening. :banghead: And roundouts are my last hope. So I have to believe they work. Good Luck

This one is a tough one. Tried a breaker bar, but I can't get it to budge...

Finally got it with someone big enough standing on the flange with the cover on the floor on a rubber mat using a socket, extension, and pipe.