Its a little plastic plug. I pulled it off and figured it was where i put my rear diff fluid in. but the fill hole is really small how is someone to check it? a finger cant fit inside the hole. Anyways its for a 94 camaro. heres the pic..

THanks!

 

That looks like the vent that is on top of the center section. The fill plug is on the RH side.
There is a pic in the article below:

http://www.bfranker.badz28.com/fbody/lubeoil.htm

 

oooh. LOL so what if i already put my gear fluid in thru the vent hole?

 

Alright i opened up the proper fill plug and i got back some of my gear oil. i guess it was overfilled cuz it did take the 2 qts from the vent hole. and from the fill hole its full. so i am assuming everything is good right?
Thanks Shoebox!