Is it possible that TT you have was designed for front end use? Maybe that could be related to the clunk. I have only peaked in one TT a long time ago but it was a casual visual so I don't know about the backlash. The part number should be scribed or lasered on the TT case somewhere.
That link about flipping the gears was not prepared by me. Actually, someone was kind enough to point it out to me so I bookmarked it.