When i broke a tooth off 3rd gear on my stock t-5 ,, the whole tooth broke off, not half the tooth or 1/4 off the tooth,, i would think if the problem was shaft flex, it would have broken part of the tooth,, I still have not read on here where someone had a problem with an Astro kit,, but im shure Atro has a limit too ,, just they hold up to thier ratings