[Mgs] 1966 OD Plug

[runner01 at wowway.com (Ray Graham)]

Folks:

I decided to change the gearbox oil in my 1966 MGB.  I have drained the main
gear box, but when I attempt to remove the OD plug which is marked "Drain" I
can't  find the correct wrench to fit.what gives?  What size is this?

 

I plan to refill with 20W50 oil.same that I run in the engine.right?
Manuals say about 2-2.5 qts. for gearbox and OD?

 

Thanks,

Ray Graham