Ok here goes
I have a 2000 F550 6speed 4.88 rear
19.5 rollback unit
Had it just over a year, 95000 miles, On local runs it does just fine 20 miles or less, on long hauls running with a load or not, temp spikes while climbing hills.
Last night I had a 2005 neon on the back for a 300 mile tow...