Ok great advice on the breather tube, I will definitely be adding that now...
I didn't really think it would be possible to overheat the diff doing autox, but this wasn't a typical autox day, it was a practice where you have unlimited runs where you can do run after run. I would have been really surprised/disappointed if it was overheating, but didn't want to rule it out after doing 6+ consecutive runs.
I think I will opt for the simpler solution of the "J" tube first to see if that remedies my problem...
That is unless spacevomit decides to craft up a series of AN tubes that do a quadruple helix followed by a spiral down through an ice cooler connected to an f-16 filter vented into the gas tank. That should be right up his alley

Don't hold out on me space, I KNOW you got the goods.