Thanks for your thoughtful reply.
I notice everything about every car I drive, and I think that is one mark
of a good driver -- rapport with the machine that is carrying you
(sometimes very fast) down the highway. So whether it's a vibration that
wasn't there before, or a sound that is not produced by the road surface,
whatever -- I notice it.
I agree with you that a rotating mass would probably be the culprit, and
that diagnosis can be difficult, on older (and newer as well) vehicles.
My definition of "slight:" Something that is noticeable but not alarming
enough to make you pull over and get out to look for the cause.
"Occasional:" Yes, just now and then. But no less real than if it were
Why do I think it was the front end? Probably two things, the direction
from which it seemed to come, and that I may have felt it through the
steering wheel. That's my best recollection.
"People notice problems with their cars after work is performed." I'm
sure they do, but the only thing I was actually looking for closely was
whether I could tell if the new control arm bushings were having a
cushioning effect on road irregularities. I wasn't looking for vibrations
of any kind.
The T-Bird (my fourth, I like 'em for several reasons) has about 95,000
miles on it. It has Monroe Sensamatic aftermarket shocks on it, and
Michelin H-rated 235-60-15 tires.
The front end work was occasioned by the fact that this car has been local
since it was first sold. Local here means rough streets, potholes,
railroad tracks, and severe front end punishment.
There was a dangerous amount of play in some front end components, and the
protective seals (or whatever you call 'em) on the ball joints were totally
shot. I considered that to be an unsafe situation.