Why is my driveshaft loose at the tail of the tranny.looks like it came out quarter inch.making car vibrate.its a 2000 with 3.8 u joints are good

 

I have a 2011, 3.7, auto trans. It took 2 years of head scratching and serious part replacement before it was discovered that the vibration I experienced was caused by the trans tail shaft flange would not seat properly against the driveshaft flange.

We are talking a very small gap resulting in a persistent vibration.