Here ya go...

My aluminum front diff on my Bravada had one.. Atleast I pulled a bolt out and it drained anyway...

 

lol, so long as nothing moves inside, it's all good to take the bolts, out, lol.

 

There was a drain on my aluminum front diff. Yours should have one as well. It's the bolt shown in the image above. On mine, it wasn't a structural bolt. I wouldn't recommend pulling structural bolts.

 

nah, mine had that nice little plastic washer under the head of the bolt, like the check plug... and it's the same size as the oil pan bolt...