Shake rattle and roll

I (and the shop) have been working hard at tryign to get the shakes and
vibrations out of my 2002 SC2. What we thought was a bad tire or untrue
alloy rimnow appeared to be a Service Bulletin issue:

00-T-57A JUN 01 Engine/Powertrain - Vibration at 48 - 54 MPH

See, the front end of my SC would shake mildly at exactly 58 mph, enough to
be annoying for an hour long drive to work. This fix required a dampener
(strut type) to be mounted from the engine to firewall to better brace the
lower engine mounts.

That fixed that issue, but now, the steering wheel vibrates at any speed
over 50 mph.
This sux, especially when driving for a straight hour to work. The tires
have been balanced already, perhaps they need rebalancing?

Has anyone encountered this SB issue? Is it now just a simple alignment/tire
balance issue? ThHhAaanNks....

 

A tire could be out of round. Have they tried moving tires back to front?

 

I shour shoulda waited before posting, lol. I took her to our other shop
which has more modern tire balancing machines, had them rebalanced. One tire
was the culprit and as the older machine could not test road force, it didnt
detect that one of my BF Goodriches has 27 lbs of road force! (I think 14+
is the acceptable margin) .

They were able to counterbalance the tire, we road tested it together and
all seems to be smooth again. Hooray for modern technology.

marx404