I have not seen nor heard of any damage to the tranny itself, usually the power dont make it to it because of the clutch/dualmass flywheel being the "weak" link
Your dual mass flywheel will eventually fail with extra hp or not. The rest of the transmission is bulletproof. You would have to run it out of oil or severely abuse it. I can tell you that bouncing excessively while sledpulling may break the output shaft.
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