Trans Temp

Allison Man.. I have a 1999 30' 165K miles Blue Bird shuttle bus I will convert to a Class A motor home. It has a pusher 5.9 24V Cummins with 4 speed Allison auto-trans and I don't have the model #. Appears that the trans has been recently rebuilt and has Dexron III oil. This increase in weight plus pulling a 25' IO boat will require me to boost the HP output 50 to 80 HP. My questions are what can I do to add longevity to the trans. First I will add a trans temp gauge so what should I expect the normal operating temp to be? I see gauges full scale 250F and others 400F what should I use? Would you recomend a synthetic oil also? Thanks for what you do. Big Hartz
Trans Temp

I don't know anything about the Allison tranny, however, my understanding is that trans temps should be between 180-200, with occasional increases to 220 when working hard. Consistent temps above 220 can cause problems. I've previously seen a fluid temp chart posted on an RV board, but I can't for the life of me remember where. Perhaps Allison can provide the info.