What revision TA brake? 17998-4, -5, -6, or -7, and the newest 17999. Some have reported cracks in the transfer channel casting due to machining mods. Here are some pics of the internals -

http://www.turboaction.com/frame.html

scroll down and find Technical Tips, and then the second grouping of links shows drawings of the internals.


Bottom line - high probability it is either the over-running clutch or the converter.

Give Paul Forte a call at TA