Well, since it's an '00 trans., then I'd change the fluid in the trans and TC, add a cooler, change filter, refill w/ fresh Mercon V, and see what you get. Not sure on the trans-go kit, never had one, so the info I have is just from other posts that I have read. I didn't want to chance it, so I just stuck w/ the j-mod. someone w/ more experience in this area should be better to suggest something.
Hopefully there isn't too much damage already, otherwise you will be looking for another trans. probably.
These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.