Tranny fluid change: how did I screw that up?

[nosfed]

Ok, I have a T5, and I've put about 15K on it since I got it in august. Yesterday, while I was doing the pins/bushings, I decided to change the tranny fluid. This should be the simplest maintenance ever, but... now when I drive the tranny clicks.

Here's what I did: with a 3/8" ratchet opened and drained from the bottom right side. Next, pumped in dextron III until it ran out of the hole left by removing the 15mm bolt with the funny spring on the driver's side. I allowed the excess to run out and put in the bolt. The guys at autozone looked it up and said it should take 2 3/4 qts, which is exactly what it did.

I feel like a dolt after this. I've done more in depth projects than I care to remember, and I can't get this right. Please help.