How about the front u joint angle and the centering of the entire drivetrain viewed from above?

Check the runout of the tires AT THE TREAD with a dial indicator.

I found a broken left motor mount..Guess the safty chain held it down, and I didn't know it broke,..but it wasn't broken when first installed,and it had the vibration..I'll get to it tomorrow..let ya'll know..

No such thing as too much !!!!!!

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but it wasn't broken when first installed,and it had the vibration

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Here is some good info - go to page 4

http://www.reillymotorsports.com/ABAR20600.pdf

Thats some good info there, thanks Lefty

The ball bearing, in the extension housing, that carries the tail shaft could be the culprit...ask me how I know. Another annoying vibration can be caused by an axle bearing. Other bearings that cause vibrations are the carrier bearings.

OK,a week has gone by and I have done everything mentioned and then some ..The vibration is definatly in the drive train..I replaced the broken motor mount.Nothing is touching or rubbing..the vibration gets worse when I get to 3000rpm and shift into neutral..worse than a normal decell in gear.Reving in neutral the motor is smooth as can be..even when decell in neutral and reving to 3k it does not effect the vibration..Now I am going to shim it up 2 dg to see if that helps..I have raised the rear trans mount for o dg coming out of the trans . I'm getting tired of this already..Just shoot me..

Sometimes you definitely have to play with pinion and transmission angles to rid of pesky vibrations.

On my 1973 Duster 340-4spd-4.10 gears I used 3 degree pinion shims in the rear and a 1/4" spacer up front to raise the tailend of the tranny.

Good luck!

Revving in neutral the engine is as smooth as can be.........is that parked or rolling about 50mph?

BOTH,parked or at 50 mph...But I'm zeroing in on the problem ...I'll keep you posted..THINK TRACTION BARS.. HERE's THE DEAL--THE TRACTION BARS I HAD ,HAVE THE SPRING PLATE AS PART OF IT..SO THE U-BOLTS BOLTED THRU THE TRACTION BAR ITS SELF..THUS TORQING THE REAR SPRINGS AND NOT LETTING THEM FLEX..I INSTALLED STOCK SPRING PLATES AND 75% OF THE VIBRATION WENT AWAY..NOW ALL I HAVE TO DO IS UNDO ALL THE SPACERS AND SHIMS AND GET EVERYTHING BACK TO WHERE THEY BELONG..DID SOME ALIGNMENT TODAY AND IMPROVED THE VIBRATION SOME MORE..GOTTA UNSPACE THE REAR TRANS MOUNT TOMORROW ...WILL KEEP YA'LL POSTED..Thanks for all the help guys..