Highway shaking

[Daltwait]

My eagle experiences a shake at 100km/hr, it's fine at 95, but anything from 95-105 doesn't feel too healthy, It was really shaky when I first bought it, so I got the tires balanced and it got a little better. Last fall I replaced a worn tie rod and took it in for an alignment.  At the shop they gave me my diagnostics and told me that they couldn't get it as aligned as they would like to, but they improved the alignment. They suspected some worn or bent component. Since it's an old car and I have a limited budget I didn't ask them to spend more time finding it. I would like to be able to find out what is causing this shaking so I can fix it and drive highway speed without any worries.
These are the diagnostics they gave me:
Before:

and After:


You can see that it's mainly my left caster that they couldn't improve. Does this give anybody any idea about what component could be bent and would cause readings like this?

Thanks in advance

[mo.eagles]

I would venture to guess they did not know how to adjust the caster.  If you go to the EPedia , How to section , Front suspension strut rods. You may need to replace those bushings to get good adjustment . Is your issue a whole car shake or a steering shake ? Check all your tires for flat spots ( caused by panic stop) . The new tires are developed for ABS and are therefor softer and flat spot easily.

[AMC of Houston]

A shake at that speed is 99%-sure a tire/wheel/balance issue.

DEFINITELY take it another (hopefully better) alignment guy.   Looks like this lazy bum only messed with the toe setting.   And if he couldn't easily tell if/what was worn; he was a hack for sure (I was a frame and alignment guy for a couple decades in my younger days).

Time for a second opinion.

[JayRamb]

Steering dampner replaced?

[Daltwait]

Checked out my strut rod bushings, they look like they could be replaced. I'll order some new ones, put them on and take it to someone else for another alignment.

[JayRamb]

I'm having the same vibration issue at top speeds. Had my suspension checked at two different places and said it was all right. It may be my strut bushings??! Dunno eeek

[AMC of Houston]

To daltwait -- If possible, use the "improved-design" strut bushings (like Moog K3090's).   They are great, and last forever.   Watch out for "normal-style" bushings in K3090 boxes tho; the US market was flooded with these via a Chinese knockoff event years ago, and some are still floating around here in the states.

To JayRamb -- Like mentioned before, high-speed vibs are 99%-sure to be some sort of wheel/balance/tire issue.   I have an old '70's-era Hunter on-the-car spin balancer that I use to diagnose this kind of issue.   Any "old-timer" shops in your area have one of those??

[JayRamb]

Awesome! Great info! Appreciated

[priya]

Hello Daltwait!
 I am Ward, Priya's husband. I was until a couple
months ago a Journeyman Automotive technician. I
did wheel alignments for ~25 years, probably about
half that time in Autobody shops where every car I
aligned had hidden bent parts and damage that I had
to find. A quick look at your readings leads me to
believe they "set the toe and let it go" so to
speak.

 First things first - a vibration that is only there
between 95-105 and feels fine at 95 SCREAMS of a
driveline imbalance. There is a tight or loose "U"
joint, "U" joints out of phase (not applicable on an
Eagle unless the shaft was modified) or the driveline
angles are messed up from a failed engine or
transmission mount, or changes at the rear differential
mounting that changed pinion angle.

 A wheel/tire imbalance would start at 80 or 90Km
or so and just get progessively worse as the
speed goes up.

 As for the alignment the left front caster is too
far positive, and both front cabers are out of
specs. The caster is adjusted at the nuts where the
strut rod goes through the bushings, the camber is
adjusted through cam bolts where the lower arms attach
to the vehicle chassis. If the adjusters are siezed
then of course the technician can not adjust them, unless
they are either taken apart if possible and made to
be adjustable again, or if need be, replaced. This will
of course not be a normal part of an alignment. The
other possibility is that the body work has a bit of a
"diamond" in it, and with the adjuster run all the way
in on one side and out on the other, that this is "as
good as it gets". On older vehicles one does see this
from time to time. Without seeing where the cams bolts
are set makes it a guess at this point.

 If you get a chance duck under the front of your car
and take pictures of the cam bolts. Post them up and
Priya will show me them. If they are at maximum adjustment
there is either some issues with the unibody
structure or bent suspension parts.

 If you want to check out the cam bolts you can but
before you touch them understand you will need another
alignment if you move them at all! When you loosen the
nut the cam bolt should be able to travel back and
forth in it's slot, and should move the lower arm in and
out with it as it travels. If the nut won't come loose,
or if the bolt will only turn a little, then "spring
back" the where it was, the cam bolt is siezed in the
bushing and will need to be freed up or replaced.

 The nuts on the strut rod typically will respond to a
large enough wrench, unless you live in the rust belt!

 If all these adjustment are movable and the cam bolts
were not at the end of their travel then you need to
find a different alignment tech! Do not go to the
cheapest place in town for your alignment. They can't
make any money doing good work for cheap, so they get
done FAST! (Set the toe and let it go - you get what
you pay for!)

 Get some pictures up of your cam bolts, from that I can
get a handle on whether or not there is an issue with
the unibody. The alignment is indeed out of specs, but
that is not your vibration issue. Give your driveline
a thorough check.
-Ward-
 

[JayRamb]

My tyranny mount is shot that could very well be it

[Daltwait]

alright here are where my cam bolts are at. Hopefully you can tell from this angle.

[AMC of Houston]

Well, looks like your lower bushings may be worn a bit. However, you still have plenty of adjustment room to get the camber to spec.   The right side is all the way out (negative), and needs to go more positive.   Left side is all the way in (positive), and needs to go negative a tad.   So the original opinion still stands; lazy alignment guy!!

[priya]

Hello DaltWait!
It's Ward, Priya's husband, popping in again:
 AMC of Houston is correct. The left front camber is out of spec positive, and
that cam is cranked all the way positive! The right front is out of spec negative
and the cam bolt is cranked all the way negative! If the cam bolts are seized
up, fine, but the alignment tech should have tried to adjust them, found them
seized, and then called you to inform you and ask if you wanted the cam
bolts freed up or replaced as required to properly perform the alignment.
 You gotta find a better alignment guy!

 Have you gone through you driveline yet to see if there's anything there that
could be your shake?

-Ward-

[1985amceagle]

I've found that the strut rods can rust away inside the bushings to where the rod and threads are significantly thinner .  My car was a MN car for part of it's life and that may have quite a bit to do with it though. As for the vibration, I would check the u joints, and if nothing can be found, have a driveshaft shop inspect the driveshaft. Also, the 1985 and later eagles the front driveshaft spins all the time due to the front axle not having a disconnect.

[JayRamb]

I posted earlier...I loosened the steering idler arm, and tightened that baby. Shaking is now gone.