t-case drain/fill plugs leak

Never had a fluid leak at the drain/fill plugs of my t-case until I changed the fluid about two weeks ago. Even after that, I didn't notice any problems until the Jeep sat over the weekend and made a small wet spot on the driveway about 3" in diameter.

The plugs were in pretty tight and I had to use a short length of pipe on the hex key to get the fill plug out, but it came out w/out any other problem. I put them back in w/out any teflon tape or thread sealer and torqued them down to 25 ft./lbs. as specified in the owners manual. Now, they leak. I tightened them down a bit more last night and they still leak.

I've read that overtightening can crack the aluminum housing because it's a steel plug. If that has happened, would I be able to see such a crack?

I'm not sure you'd be able to see the crack, but if you clean the fluid and dirt off the case around the plug very carefully just after parking it, you should be able to see where the leak is coming from better, or at least be able to tell how far up it is.