Now, I've run into another situation that does not seem right. The
gearbox on my post hole digger has never been used. It was stored for
about 6 years.

When (about a month ago) I decided to assemble it, I added a teacup of
90w gearoil to the gearbox. (the label said it was dry, add oil) I only
put that small amount in order to flush out any debris that may have
accumulated while in storage.

Today, when I opened the drain to flush out the oil, so as to add new,
the plug popped out, the oil was under pressure.

Which brings up my questions... Should there be a relief hole in the
box? If not, won't the pressure rupture the seals?

Help, I'm treading in unknown waters, here!

Leo (pearland, tx)