Hello,

What would cause an EXTENSION TAIL HOUSING on a 1996 F150 4wd auto transmission to break. And what else could be wrong?

 

Driveline vibration. I snapped mine off on a high speed pass when the drive line went off center axis and basically started jump roping under the truck. It snapped just before the mounting flange where the extension housing mounts to the tranny.

Oh crap... just realized it 4wd. Not sure but could be the same reason...lol