My rolls royce has a vibration at 80 to 90 miles an hour.  The tires,
motor mounts, the transmission and drive shaft have all been checked
and found O K.  Any suggestions.

What year is it?

And is this a new phenomenon or has the problem been there for the
enirety of your ownership?

Note: this is a duplicate question.  Wildwolf -- if you don't intend
to have 2 questions posted, you may wish to cancel one of them.

Best regards,

Omnivorous-GA