Vibrations

[Dennis Ruffing <altia!dennisr@uucp-1.csn.net>]

Keith,

I read with interest your description of vibrations in your v8.

> My 1990 V8 (56,000 miles) has recently developed  some vibration in the
> steering wheel after especially  after a cold start. It is especially
> noticable going uphill.  I notice it most with tiny steering corrections.

I have an 88 90 (fwd) which exhibits the same basic problem and has
for about two years.  Of course, I'm sitting at 196k miles, not 56k.  

I don't have the solution for you, but I will share my experiences
tracking it down, and maybe one of the list's resident suspension 
experts would care to comment.

STEADIRIC, HELP!

In the last two years, I've had a fair amount of suspension work done.
Both mechanics I've had it to for other work have always had a kind
of "geeze, I don't know" attitude towards it.  I want to solve it.

The vibrations were always present (and annoying) no matter the allignment
and wheel balancing.  There has always been a single "cronk"
noise under first gear acceleration or anything else that results in
more torque being applied- Colorado's long, mountainous climbs really
bring it out at highway speeds.

Here's what I've done so far, followed by my next steps:

Shocks- including strut bearings and control arm bushings.
While the shocks made a difference and the mechanic indicated
that the control arm bushings were shot, I noticed only and imporvement
in the spring of the car.  The cronk was still there, vibrations and 
harshness.

Tie rod ends- They improved the tightness of the steering, but the 
cronk was still there.

Ball joints- closer.  The ride continued to get tighter and smoother; I
highly recommend new ball joints on older cars and have developed enough
sensitivity to distinguish ball joints harshness from bad shocks.  But
still the acceleration vibrations and the "cronk"

Engine Mount, transmission- Well, there went a hundred bucks on something
I didn't notice a difference.  Stil the cronk.  Still the vibrations

Tightening sway bar- Here I thought I was on to something.  One of the 
sway bar mounts was a bit loose.  I tightened it up and.... no improvement.

Here's my theory:  something is loose enough to let parts of the suspension
shift under a heavy load.  Shift is a strong word; perhaps it should be flex.
In any case, under heavy loads, accelerating from stop, climbing hills, the
suspension goes under enough of a shift (or flex) that the geometry is
effectively changed and the resultant vibrations (and my cronk) appear.  The
only thing I can think to do is to keep replacing suspension parts; bushings
first, mechanicals later.  Unless anyone out there has actually had and 
solved this problem before?

My next step is to find out about replacing the sub-frame bushings;
Does anyone recommend a source for them; are there urethane ones 
available?  Can I do this in the driveway or will the engine
have to be held up?

After that, Sway bar bushings- same question of source and urethane.

After that, I'm not sure what's left in the suspension.  The steering
rack is fine.  Everything else will have been replaced.

Can CV joints eventually wear to the point that the drive shaft has a 
bit more rotational play in it than it should?

Are there other common engine mount issues that I should tackle?

The car is improving and getting tighter.  I just want the vibrations
solved.

Thanks for the help and I hope this helps you start down the road
to a tight and smooth V8 suspension.

Audiex,

Dennis Ruffing
dennisr@altia.com