BA10/5 Fill Plug...what tool?

Guys, trying to check the fluids in my son's 87YJ with Peugoet trans. I cant seem to find the proper tool to pull the fill plug.

1/4" ratchet is too small and 3/8" ratchet is too big. What gives? It's a square hole and i even tried a few allens without luck.

It's metric...8mm or something like that? It's come up a few times around here and while one of the tool trucks actually has a part that fits, the concensus seems to be to just grind down a 1/2"-3/8" adapter and use that.

It's 8m/m or 5/16" square drive (both are about the same size.) The quick and easy way to make one is to take a cheap 8m/m or 5/16" hex key and grind down two opposite corners to make it fit in the square hole. That's how I end up doing it. After all, why waste a perfectly good adapter or extension? I need those...

5-90

Thanks Guys....son is on his way to Sears Hardware. :laugh3:

I remember helping someone out with this, I got a piece of square 8mm stock from NAPA and shoved it in there, then used a crescent wrench on that. Come to think of it, that square bar fit snugly into a 12 point socket. Filing down a 3/8 drive would work though.