Well buddy just got his 4l80 swap done. The trans was built by YANK for dyno testing of a few vehicles. the trans has a manual valve body and a 2800 converter. The problem is the tailshaft seal keeps pushing out and leaking.The seall isnt tearing, just pushing out of the recess towards the yoke. MY bud says he can feel a vibration at 80-90mph. The trans only has dyno time on it, the driveshaft is a brand new unit built by driveline specialist of LA. new yokes and U joints. His mechanic says he thinks the tailshaft may be bent. I have not looked or seen the problem but to me it sounds like a pressure related problem. Anyone heard of bening shafts or does it sound like a pressure problem? Truck is 02 chevy single cab. procharged 6.0 built by Futral Motorsports.