I can do back to back runs down the track, and my trans temp will barely move. but, If I'm cruising down the highway at 75mph in 6th gear, my temps will increase rapidly. I've seen 220 degrees on mine. makes me nervous, but everyone I've talked to says that 250 is the danger point, and not to sweat seeing 220.

I know there's a lot of plastic in the trans though, and plastic does not like heat. (needle bearing cages, thrust washers, etc. made from plastic)