56 Cadi vibration

[56Cadi]

I have  56 Cadillac with a severe drive line vibration. The vibration starts just above idle and is very bad up through mid rpm and seems to become less at high rpm. The vibration is both during driving and or sitting in neutral or park.  I have checked all the obvious the balancer, engine mounts, trans mounts which are all appear to be fine.  I've also done a engine compression test and complete engine tune up.  I have also eliminated the accessories i.e. PS, AC, generator.  Can anyone advise of what may be the problem, I suspect it may be the transmission. I bought this car several months ago which came with a receipt for a rebuilt trans appox 6K mi ago. HELP!!

A. Brocato

[jaxops]

I had a similar problem with my 56 Series 75, and it turned out to be the driveshaft support was badly worn inside and allowed the shaft too much "run-out" causing the vibration.  Something to check anyway!  I also replaced the driveshaft while I was at it.  It just seemed a bit out of round.

[56Cadi]

This car does not have a carrier bearing and as noted the vibration is present in park or nuetral!

[russ austin]

The harmonic balancer could have slipped on its hub. May look good, but lts out of balance.

[J. Gomez]

Have you checked Roger’s recommendation on your second post, http://forums.cadillaclasalleclub.org/index.php?topic=126383.0 those are good starting points to start.

Also as an alternative checked point, checked the motor mounts, just do not trust the outside look.

Good luck..!