I just had a turbo 400 and a shortened steel driveshaft put in and at around 3600 to 4500 rpms there is a huge vibration. I have had the driveshaft balanced twice and it's perfect. The only other problem is that the driveshaft has a little play in the tailshaft of the tranny. Could this be the whole problem? Also what is needed to repair. Thanks in advance

 

Read through this thread, may have to do with Drive Shaft Critical speed.

https://ls1tech.com/forums/conversions-swaps/473265-u-joint-angle-question.html

Hope that helps

Pat

 

You can try a new bushing and seal in the tail housing. If this is your problem chances are you have other worn bushings in that unit. I would also look at drive shaft angle. Most vibrations are caused by this!

 

Thanks stu cool and da wrench