98 V79 NA front end vibration (control arms replaced) Topic is solved

[sleddriver]

OP: Have you had your 4-wheel alignment done yet?

Did it help the vibration problem?

[98v70dad]

OP: Have you had your 4-wheel alignment done yet?

Did it help the vibration problem?

No, I havent. I live in metro Atlanta and spend almost all of my weekday free time in traffic. I also am a diyer and I have a big backlog of things to finish on the weekends. I offered to help a friend screen her porch and that has taken up the better part of three saturdays.

Anyhow, I saved all of the tires that came off of my car and they are worn perfectly evenly. The ones on the back had been on the back for 4.5 years. They are worn down to half of the tread but are evenly worn. I doubt they would be like that if the car was badly out of alignment. Its something I do plan to check up on though.

One thing that may have contributed to my vibration that I havent mentioned is this: I got stuck in the mud in my back yard about 8 months ago. (lesson learned - dont park your car off the end of the driveway on new fill) To gain traction I put an oak log from my wood pile in front of both wheels and hit them both with a sledge hammer to wedge them up against the tire. Then I got in and gunned it while the wheels spun. Suddenly, one or both of the logs engaged with the spinning tire and the car flung them rearward. I dont know what they hit but a month later I noted the torn boot on the drivers side axle. On the passenger side I don't know if it hit anything but maybe it hit that long axle long enough to bend it a bit. Given the geometry it seems unlikely but I suppose its possible by rebound bouncing forward off the subframe. I do remember a loud thud from the impact. Maybe it hit and bent the control rod although it looks straight. This is something I need to investigate further. I had forgotten all about this but remembered it driving home yesterday.

One thing that I have noticed is that this vibration doesn't happen every time I drive the car and it seems to be closely related to the temperature. I can drive 37 miles to work at 6 AM and around 70 degrees with no or nearly no vibration for the whole trip. In the afternoon lately the dash thermometer tells me that its 97 F. The car will vibrate the whole way home in the afternoon if I run it at about 67 mph. In the morning I can run it at that speed for the entire trip with nothing or nearly nothing. I'm wondering if the colder morning temps make the grease viscous enough to damp any vibration in the CV joint. Thoughts?

[misha]

Rubber bushings?
They are more temperature sensitive than anything else.
Shock apsorbers too.Stiff on cold and softer on warm weather.

[98v70dad]

Rubber bushings?
They are more temperature sensitive than anything else.
Shock apsorbers too.Stiff on cold and softer on warm weather.

Shocks are less than two years old. Bilsteins. Subframe bushings are originals.

[beigg]

I dont know what they hit but a month later I noted the torn boot on the drivers side axle. On the passenger side I don't know if it hit anything but maybe it hit that long axle long enough to bend it a bit.

Thoughts?

Did you replace the entire axle with a good non compromised axle assembly?

[sleddriver]

One thing that I have noticed is that this vibration doesn't happen every time I drive the car and it seems to be closely related to the temperature. I can drive 37 miles to work at 6 AM and around 70 degrees with no or nearly no vibration for the whole trip. In the afternoon lately the dash thermometer tells me that its 97 F. The car will vibrate the whole way home in the afternoon if I run it at about 67 mph. In the morning I can run it at that speed for the entire trip with nothing or nearly nothing. I'm wondering if the colder morning temps make the grease viscous enough to damp any vibration in the CV joint. Thoughts?

After recently posting my notes on hydraulic mount replacement, it got me to thinking about vibration from another angle:

Worn out sub-frame bushings.

The steering rack, motor and front suspension is all mounted on the sub-frame. Thus all vibration from such travels to the unibody via the SFB'ngs. Mine are now 19yrs old. No doubt they are hard-as-a-rock and crumbling in some places I can't even see.

I was very surprised to learn these things are quite similar to the upper spring seats: There's a steel collar in the center where the bolts go through and rubber/silicone/compound surrounding it to form the "donut". Over time I wonder if, in the vertical plane, steel-upon-steel contact occurs between the SB and the uni-body, which would be a great NVH conductor.

Furthermore, I was also surprised at the overall positive ride-quality-benefit from replacing both hydraulic mounts, as they hold up the motor not the suspension. I have new Sachs shocks/struts that are maybe two/three years old. So I was quite surprised at the overall improvement due to these MMs.

In my continuing effort to "guild the sled", I'll have to consider SFB replacement......

[98v70dad]

One thing that I have noticed is that this vibration doesn't happen every time I drive the car and it seems to be closely related to the temperature. I can drive 37 miles to work at 6 AM and around 70 degrees with no or nearly no vibration for the whole trip. In the afternoon lately the dash thermometer tells me that its 97 F. The car will vibrate the whole way home in the afternoon if I run it at about 67 mph. In the morning I can run it at that speed for the entire trip with nothing or nearly nothing. I'm wondering if the colder morning temps make the grease viscous enough to damp any vibration in the CV joint. Thoughts?

After recently posting my notes on hydraulic mount replacement, it got me to thinking about vibration from another angle:

Worn out sub-frame bushings.

The steering rack, motor and front suspension is all mounted on the sub-frame. Thus all vibration from such travels to the unibody via the SFB'ngs. Mine are now 19yrs old. No doubt they are hard-as-a-rock and crumbling in some places I can't even see.

I was very surprised to learn these things are quite similar to the upper spring seats: There's a steel collar in the center where the bolts go through and rubber/silicone/compound surrounding it to form the "donut". Over time I wonder if, in the vertical plane, steel-upon-steel contact occurs between the SB and the uni-body, which would be a great NVH conductor.

Furthermore, I was also surprised at the overall positive ride-quality-benefit from replacing both hydraulic mounts, as they hold up the motor not the suspension. I have new Sachs shocks/struts that are maybe two/three years old. So I was quite surprised at the overall improvement due to these MMs.

In my continuing effort to "guild the sled", I'll have to consider SFB replacement......

I've got a background droning vibration (probably due to shot frame bushings and/or hydraulic engine mounts) on top of the out of balanced tire feel vibration. I would be quick to diagnose my "out of balance tire" vibration as being due to an out of balance tire except that it only happens sometimes and is temperature dependent and the tires have been balanced 3 times.

I noticed yesterday that my transmission fluid is a little over-full when hot. I don't know if that contributes or not. I doubt it, but maybe. I plan to get that corrected tomorrow.

Thanks for the info. I may add the frame bushings to my list and based on the relative ease of installation and lower cost I might do those first.

[kcodyjr]

Hm. the 65-70mph speed range really is characteristic of a control arm problem.

Did you check the ball joints as well as the bushings?

Also, don't discount the 4 rear bushings. In these cars, rear wheel play *is* a steering input.

[98v70dad]

Hm. the 65-70mph speed range really is characteristic of a control arm problem.

Did you check the ball joints as well as the bushings?

Also, don't discount the 4 rear bushings. In these cars, rear wheel play *is* a steering input.

Thanks. The control arms are originals but they dont wobble at all in the push pull test. They are the only thing in the front end suspension I havent replaced. Maybe I should focus on them.... I didn't know about rear end bushings. I need to educate myself on that....

[misha]

No you don't.
If the bushings and ball joint on front control arms have no play....leave them alone.Why you would like to replace something which tested ok?!

If in any case you have play in rear bushings you would have vibrations at REAR end...NOT FRONT end.

Allignment have nothing to do with any kind of vibrations...especially with steering wheel vibrations.It just affects handling and eats tyres prematurely.

About rear bushings.....i never seen ones fail....YET.But if they would fail they would make clonks and similiar sound...just like front ones would.

After all...we are back to the begining.....aftermarket axle or bad wheels out of balance.

If tyres are not balanced ok it is more noticeable in higher speeds.Up to 60km/h you don't even need balance of good tyres...(i was told by a reputable tyre installer).