If you buy one from transtar, request that they pack the box with padding of some sort, I got lucky, they threw mine in a triwall cardboard box and mailed it to me rattling around like a ball in a pinball machine, but it still got to me in OK shape. I'm not the only guy this has happened to, either: http://www.pirate4x4.com/forum/showthread.php?t=690054#5
Like the other guys said though, are you sure it's the TC?
This has been an ongoing saga for a full year now.
I have replaced every Item that is remotely related to the Trans except the TC and still have the same Issue.
I loose Overdrive Lock up after Temps get above 210 for about 20 miles.
I loose Overdrive Lockup if I give it alot of gas, say pass another Vehicle