Well I just did control arm, sway bar and large and small bushing on the lower engine mount on my 2011 MCS. I know the street poly bushing from powerflex will cause the car to have more vibrations when at idle from the stiffer motor mount. The vibration are not bad to me at idle and once I start moving it goes back to stock feeling. Well today i may or may not have hit triple digits in speed and that's when I started to feel vibrations. Before the bushings at those speeds the car felt the same as it would be at highway speeds. I'm going to look and see if I lost a wheel weight and get tires rebalance but I'm curious if the poly bushings on the lower motor mout will cause vibrations at high speeds? I wouldn't think so but that is all I have done to the car since the last time I've hit high speeds. And yes lugs are tight. Thanks .

 

I’m assuming all of the bushings you
did were the street (regular) Powerflex
ones, not the black racing ones nor
oem ones.

I doubt the engine mount bushings
would do this, and also wouldn’t be
inclined to blame the front control
arm bushings either.

Agree with rebalancing the tires first,
and also rechecking alignment,
especially front toe-in.

 

Yeah they are the street bushings I wouldn't think the bushings would be the Issue But like I said the bushings were the only thing that I have done since the last time I was at high Speeds. I Did not even think about an alignment I wouldn't think it would be off from dropping the sub frame because I didn't mess with camber plates or tie rods other than unboltimg them from the knuckle.

 

No, dropping the subframe then
bolting it back up usually doesn’t
mess up the alignment (could shift
camber up on one side and down
on the other, but there’s usually
not enough play in the mounting
positions to do that significantly).

On the other hand, old worn control
arm bushings can give you unstable
toe readings. Setting it can be like
hitting a moving target, and when you
put the new ones in, it ends up solid
and stable, but not quite where you
thought it was before.