Hi Wil,

    As Jim said it is a 17 mm allen. And most good FLAPS have them. If you
have trouble finding one, a quick fix is to take two 10 mm nuts and put them
on a bolt and weld them to it. Use the bolt/nuts as the allen. Engine to
transmission top bolts are the right size.
    Hope that helps, maybe get you out of a bind. Not to be redundant, but
make sure the car is sitting level when checked.

Howard

Subject: gear oil fill bolt in tranny?