Hey folks I have and Allison 4000 and Cummins ISX/15Liire/525HP in "03 Sig.........my "normal" operating tranny temperature range is 210F to 230F / no issues - ever, that's why I changed to Transynd Synthetic, to ensure it I don't have issues and of course; verified all of this with my Allison authorized factory representatives.
Big Engine, Big Tranny, Big Coach (47,000Lbs)......lots of heat and I didn't want issues \ in mountains or flat-landing, I watch trans temps carefully while traveling to ensure I never do have issues!
Remember when asking the question about "normal" operating conditions: everything is relative, OK? Malcolm