Same crank, same trans, same converter that you have ALWAYS run, with no issues. So look at it logically. Did the converter to crank hub fitment suddenly change? Highly unlikely.......So what else was changed? You freshened motor and trans. So looking at it from that standpoint, you either set the thrust up WAY tight or something in the trans is not letting the converter exhaust the fluid fast enough............Or, like I said, the element in converter COULD be going away, but I am still betting something in trans. Ten year old converter though, so it sure wouldn't hurt to have it looked at and freshened

Monte