I don't this so.I'm wondering too if it is not something the alignment shop did?
they would have loosened the locknuts on the new upper control arms for instance (as well as the steering links) to adjust castor and tow in etc.......did they also tighten the lock nuts back up?
Jacking up the rear changes your driveshaft geometry so I think Ed has pointed you in the right direction. I too, have a curious vibration that I believe is in the drivetrain somewhere. I just downloaded an article on drivetrain geometry and it talks about symptoms under load, no load, decel, etc. and will pinpoint what angle is off. I am going to try shiming the center bushing to see it the symptoms change.Firstly,
I want to thank everyone for their help. I am stumped on this one and need all the help I can get. So thank you again.
I just performed a little experiment that I hope will help.
I raised the back of the car and put on jack stands. Removed the wheels. Ran the car up to 4th gear and 3750 RPM where the trouble is. NO vibration.
I then put the wheels back on, car still up on jacks and did the same. NO vibration.
I think this tells me that the driveshaft is good. Does it also rule out the differential?
I have balanced and re-balanced and put several sets of tires on with no change (meaning that there is a vibration), so I think that tells me its not the tires.
I think the only things left:
Front Bearings I changed at the end of last season
Front or Rear suspension part (I replaced the front upper control arm, still vibration)
Rear Bearings I changed at the end of last season
Removed and replaced the differential friction disks, but I think my experiment rules out the differential?
What do you think?
Thank you in advance,