I have not seen any durability issues with the 10 speed behind the 7.3 yet. I wouldn't say that my trans hunts for gears at all. The only annoying thing I've found is the 3-5 shift when I'm easy on the gas pedal. With no load I bet I only see it use second and 4th gear maybe 8% of the time. I am running 4.30 gears though so it may be different with other ratios. Even towing out west with my heavy load, in 103 degree heat on those steep grades I only saw my trans get to 238 for a minute or two. Around town empty the temp stays right at 205-217 I guess that new ULV fluid is designed to run at that temp. With no trans cooler out front (just the liquid to liquid cooler next to the trans) it really does a good job keeping the temps in line.