I have a bad drive train vibration from about 2800 rpm up..Heres what i've done..it's a 440 with t-flight,8 3/4rear..motor is smooth in neutral. I have 2 converters.stock and 3000 stall.no change..stock drive shaft,and 3 + inch shaft custom made and both balanced as I had to have them stortened for my install.I have 2 center sections for the rear, one has 3:91 gear the other 2:76 open for road trips..that was the original 741 chunk that came with the rear housing, the other is a 489 with posi.Vibration with any combo is at 2800,tires balanced a few times plus another set,plus the Hoosiers.I'm out of things to try..feels like drive shaft type of vibration.I have gone from down 2 dg to o dg to up 2 dg on the pinion angle.Any ideas ???PLEASE READ MY LAST POST FOR THE RESULTS ..VIBRATION IS ALMOST GONE,THANKS EVERYONE FOR YOUR HELP.