mystery front suspension vibration

[hoju1301]

Im having a front steering vibration from the front left suspension. Tension rods, kingpin, upperlink, control arm was replaced within the last 15k, the kingpin less than 5k

ago, and had to be replaced twice by the dealer (waranteed). The rack was so worn it started to click and tehre was plenty of steering play so that was just recently changed by the dealer with a new factory rack.

The "jiggleness" is gone but the vibration is even worse now! Steering effort/preload is a lot stiffer now as well. The steering wheel has a slight transition from left/right steering but that is from the pinion gear?

This vibration started when i replaced both lower control arms. Everything was double checked and torqued to the correct specs. Even the dealer went over this car twice over and could not find the problem.

Now there it also clunks when hitting moderatly sized bumps as well (going straight or turned) , and also clunks when moving in/out of my driveway at an angle.

This is really mystifying me...

[maxnix]

Haven't mentioned shock absorbers and its associated rubber.

Did they adjust the steering rack, or just bolt it one with new mounting rubber and boots? What was the condition of the fluid in the pump?

[hoju1301]

shocks were replaced also about 15k ago, top hat rubber hasnt been replaced yet..

[Q45tech]

[6] Sway bar bushings, new end links, wheel bearings, hub, rotors in spec?

I always change wheel bearings with kingpin and its 2 bearings.....the third link [socket for king pin] may be worn.

Front left [do you mean passenger side] always wears worse and faster due to road edge roughness?

[hoju1301]

new wheel bearings and steering knuckle as well...this vibration wasnt there until i changed the control arms to new ones...maybe some tapered joint is loose somewhere? Oh the tires (new firestone SZ's) were balanced with a 9700 recently as well.

[hoju1301]

im going to get a dial indicator and stand today and will measure play as per service manual and post on here. what are the typical frequencies corresponding to different vibrating things on a car? I might have access to a digital scope with a FFT plugin and a accelerometer.

[Q45tech]

If it is a tire or bent wheel or warped rotor .......1st harmonic fundamental will be 13.3 Hz [+- 0.3 Hz] at 60 mph [speed inaccuracy will change frequency as will non perfect rolling diameters of tires] should show 2nd and 3rd harmonics also: 26.6 & 40 Hz.

The amplitude of the various frequencies would be helpful.

Watch out as both front tires may be involved and the frequecies/amplitude will be different as they phase in and out!

What was the radial force imbalance on the SZ tires under 5 pounds would be excellant 10 pounds acceptable.

[hoju1301]

the radial force for all the tires were less than 10lb variation. I'm still waiting for the dial indicator/stand to arrive, will let everyone know the results on friday.

[Q45tech]

Some of it may be that you got use to the loose suspension and now tightening it up [new parts] is letting the road vibrations thru.

Does the vibration change phase [come and go] in a 1/2-1 second period does the quite period interval change with speed. Does it change as the tires warm up.

The SZ-50 are no where near as smooth as the Michelins [sidewall stiffness].

My first guess after tires is the rotors [runout]. It is very difficult for me to keep mine in spec..........even with runout shims and starting with under 0.001" mine get to 0.003 in less than 6,000 miles. Most are not sensitive enough to feel the 13 Hz [single point warp] till over 0.006" but the factory spec is 0.0028".

Does the vibration change [at 60 mph] when you lightly touch the brakes mainting foot on accelerator.

In ATL they use rough drain promoting asphalt, this road surface promotes vibration with directional [heel toe feathered] tires that is unknown with non directional Michelin H4 on the same car.

I switched back and forth between V4 and H4 in same size multiple times to isolate this.

[Q451990]

shocks were replaced also about 15k ago, top hat rubber hasnt been replaced yet..

I had a noise that sounded like a receiver-type trailer hitch with something in tow. It turned out to be bad bump stops and rubber at the top of the shock assembly. Not really a vibration, but more of a loosnes and rattle when going over some bumps and rough road surfaces - typically at lower speeds.

Heath

[natsoundup]

The rubber in my drivers side obliterated for some reason.... caused a rattle. So I replaced that top hat... I think about 38 dollars for the part... I took out the strut...and had a shot compress the spring and put the new top hat on.

Replaced it...now it's fine.... passenger side is fine...go figure.

This was in the 90

[hoju1301]

okay went for a test drive...still clunking in front left suspension (drivers side). vibration gets worse on roads with a rough suraface texture and is pretty bad. I hooked up a analog adxl 1channel accelerometer, and used the soundcard on my laptop. aligned sensing axis inline/parallel with the axis of the rack and pinion (attached to tie rods with epoxy as recormended by Endevo's guidlines for accelerometer mounting). vibration at 23Hz, but might not be accurate because accuracy goes to crap below 35hz on the integrated sound card. will verify with a function generator tounight and post.

for the procedure as per service manual, is it critical to apply the specified force with that special tool to measure the play in the linkages?

vibration seems to get better randomly sort of probably due to road surface roughness, but can be felt from as low as 15mph, sometimes better at 75, way worse at anything above 80.

thanks again everyone!

[Q45tech]

Lap top sound cards have terrible frequency responces.

Pico Tech makes a wonderful A/D and free software that uses parallel port .http://www.picotech.com/dso_sp....html

Look at other less expensive versions but you need at least 12 bit accuracy.

The 23 HZ is useless without knowing engine rpm and road speed and tire diameter/size ...............did the frequecy change as you changed road speed?

[hoju1301]

still waiting for friend to get his digital scope....laptop measurement was way off (no surprise cause of the crap sound card). would a good sound card suffice (terratec dmx 6 fire, or a m-audio)? im looking at getting the AD212 from pico, but 12 bits is slightly limited, and the price diff to the 216 is almost twice the price...any other DAQ you would reccormend?

did some measurements with dial indicatorrotor runout 0.001" (theyre almost brand new)hub runout 0.002" (hub isnt new, but bearings were replaced)upperlink/3rd link play 0.005" (3kmiles on the upper links)upperlink/frame play 0.004"play between lower control arm/steering knuckle where that tapered joint to the ball joint is 0.05"---alignment specs done after rack replacement few days ago--camber -1.1caster 7.0toe .06----tightened the nut from the control arm/knuckle to the torque spec. still makes a clunking noise when backing out of my driveway or hitting those little road reflectors. steering wheel vibration is slightly less.

very small audiable click when pressing on hub downward, but havnt been able to reproduce it consistantly, and its a very soft clicking sound, but same sound but much louder when backing out of my driveway/hitting bumps.

both the control arms and knuckle are new. hopefully that tapered joint isnt deformed/worn. dealer replaced all these components along with kingpin. will take apart and inspect as well.