Moronic newbie question

[zing]

What is the item on the left rear which I circled in this picture?

Just though I would follow up on this one, in case anyone else is looking for the same thing. dcyrilc, you were absolutely correct and you win the big prize, because that was it. I managed to get a pipe wrench onto it and open the cap, stick a piece of straw down into it and low and behold it came back red. Had to get a littel funnel that I could jam in place so I could fill it, but about a gallon topped the tranny fluid back up to the top of the fill on the dipstick.

Big releif to get that topped up and not have it sitting so low anymore.