Friend of mine has a 7.3 with a small tune in it. ZERO trans problems. Motor problems, no trans problems. Call an allison silly but anybody thats gonna tune a diesel to make serious power, which is easy, knows you need a trans. When i had my duramax and someone rolled on me whether it be chevy ford or dodge, my only question was you have a built trans? answer was always no and i always beat the poop out of them... you're not running a 275 tune without a built transmission...if you are i call you...grandma.. I beat the crap out of mine at the strip, pulling trailers and it finally let me down after 40k, if you think you can do that on a stock trans.....well, you're wrong. I had a 13 foot enclosed trailer at 127 and out ran a honda, you're not doing that on a stock trans no matter what the make.
i know the allison is a solid trans just like all the other ones, they are designed for the manufacturers ratings. when you double that with a 750 dollar tune, they are not gonna last. period.