Driveshaft question

Usually when the housing breaks it’s because of an out of balance driveshaft.
Too long and they jam the trans internals together causing end play clearances to go away and smashing parts together.

Lol, this was 1/4 mile, B-body Dart, with a 426 hemi grafted in.
I knew he solved the issue, didn't hear the cause .
Prob 2nd gear shift.
Thanks.