727 or 904?

You have completely missed what I said about the traction issue.
That is another way that the sprague can fail. The tires grip, ungrip and then regrip again.This can shock the sprague and fail it. Nothing to do with the burnout. That is why some trans brake makers believe you should have low band apply to protect the sprague.
this was not for you it was for rusty and his coment about starting is 2nt gear. With my 340 I could NOT start in 2nt gear.
I agree that a slip and grip could fail a sprag if it happen in 1 gear launch. not arguing here.