The last stubborn vibration left on my Lumina...

[ptcfast2]

I've normally been able to find solutions to various problems involving my Lumina by lurking around, but I'm having a hard time figuring this one out!

 

Here's the scoop: I'm the proud owner of a 1998 Lumina 3.1 with about 234,000 miles on the odometer. I've spent the past 2 years replacing part after part trying to get her (almost) as good as new. As long as I've owned this car I've had vibration problems. I started to tackle them about a year ago by replacing anything and everything related to my suspension/wheels with new parts:

 

-CV Joints

-Front Wheel Bearings

-All 4 Struts

-Inner/Outer Tie Rods

-Balljoints

-Subframe Mounts

-Swaybar Bushings

-Trailing Arms

-Lower Engine Mount & Transmission Mount

-Front Dogbone Mounts(or w/e they are called )

-New Calipers, Rotors, Drums, Pads

-4 New Tires (Aligned & Balanced Twice!)

-Transmission was rebuilt about 3,000 miles ago

 

The ONLY vibration left is one that occurs between 65-80MPH. It will come and go when I hit bumps between 65-80MPH (it almost seems like something gets knocked loose and gets bumped back into place later). The vibration is most noticeable in the driver's side footwell/floor and it can be felt slightly in the steering column. I've verified that it is not the tire as it occurs with any other tire I try. I've also noticed a loud "clunk" when breaking hard from a high speed (it's occasional - not able to reproduce every time). The clunk seems to originate from the same location as the footwell/floor vibration.

 

I've verified the sway bar bushing bolts, checked for play, verified torque on the drive axle nut and wheel, caliper is not loose. I just replaced the CV axle on the driver's side due to shudder/vibration upon acceleration (it's gone now! ) as well as the balljoint...the one I put on a year ago already failed!

 

Any idea guys? This is driving me crazy!

Edited April 23, 2011 by ptcfast2

[alec_b]

You say you had the tires balanced twice, were they just static balanced? If so, I have three words for you: ROAD FORCE BALANCE. Gm vehicles are terrible with having vibration issues if the tires aren't perfectly balanced, and a road force balance is the only way to get them 99% perfect. It involves matching the "heavy" spot on the tire to the "heavy" spot on the rim and then using weights for the subtle remaining balance. Works wonders for stubborn vibrations.

[Night Fury]

Steering rack loose?

[ptcfast2]

You say you had the tires balanced twice, were they just static balanced? If so, I have three words for you: ROAD FORCE BALANCE. Gm vehicles are terrible with having vibration issues if the tires aren't perfectly balanced, and a road force balance is the only way to get them 99% perfect. It involves matching the "heavy" spot on the tire to the "heavy" spot on the rim and then using weights for the subtle remaining balance. Works wonders for stubborn vibrations.

 

Call me crazy, but I would think that if the noise only happens on a certain side with all 4 tires (I've rotated all 4 tires in) it's not tire related? Or I could just have really bad luck!

 

Steering rack loose?

 

I was thinking it might be rack related. Besides the inner tie rods I've never actually done anything to it, so it would make sense that the problem was emanating from there. Is it common for it to become loose over time? Anything I should specifically look for while I'm down there? I'm a novice self-taught mechanic thanks to this car, so I learn about what I'm working by looking at the GM service manuals and just dive in...

[Night Fury]

Yeah seems to be pretty common. I think normally it causes a clunk rather than vibration, but you never know. Worth checking, since it's free to do so.

 

Just check the bolts that mount it to the firewall/frame

[alec_b]

Rack actually makes a lot of sense. The bushings do wear out over time, and no amount of new inner/outer tie rods will make it better. A quick look with a flashlight should make it pretty obvious whether they're worn out or not.

 

The vibration in the floor really sounds like wheel bearing to me, although you said you replaced them. What brand did you use? Were they cheapies?

[dodgethis]

I agree with the vibrations in regard to the possibility of it being wheel bearings. I recently had my front wheel bearings replaced, and while i don't hear a constant hum at low speeds, it is noticeable in the car at interstate speeds, its kinda annoying, but the only why to fix that is to just replace the wheel bearings. I am too cheap for that.

[ptcfast2]

Yeah seems to be pretty common. I think normally it causes a clunk rather than vibration, but you never know. Worth checking, since it's free to do so.

 

Just check the bolts that mount it to the firewall/frame

 

I checked the mounting bolts for the rack and they seem as tight as they ever were. I actually couldn't move them and I would of had to break out the breaker bar it seems. The drivers side bolt does not seem to have a bushing but the passenger side one does. Upon further research it seems only the passenger side bolt is supposed to have a rubber bushing insert (Service manual seems to confirm this) . The frame bolt on that side is as tight as I left it when I replaced it about 6 months ago. I pushed up and down on the car from underneath to see if anything seemed loose...it all feels/looks solid.

 

Rack actually makes a lot of sense. The bushings do wear out over time, and no amount of new inner/outer tie rods will make it better. A quick look with a flashlight should make it pretty obvious whether they're worn out or not.

 

The vibration in the floor really sounds like wheel bearing to me, although you said you replaced them. What brand did you use? Were they cheapies?

 

From what I recall....NTP bearings from Advance. Can't find the receipt for them, but I'm not one to rule that they aren't the cause of the problem. I think they can be classified as a cheapie brand (I was new to doing my own work on cars when I bought them - finally learned all the good brands!). The passenger side started to emanate a howl/whine when moving just a few days ago...it's gone for now but I think it may return soon. Sounded like a bearing....

 

Something to note: If I hit a large bump when the vibration is occurring (Over 70mph) it will disappear...and return after a few seconds. Rinse and repeat.

 

I agree with the vibrations in regard to the possibility of it being wheel bearings. I recently had my front wheel bearings replaced, and while i don't hear a constant hum at low speeds, it is noticeable in the car at interstate speeds, its kinda annoying, but the only why to fix that is to just replace the wheel bearings. I am too cheap for that.

 

Were the vibrations constant or would they come and go if you hit a bump or something? Was it more of a floorboard vibration or could you feel it in the wheel more?

Edited April 24, 2011 by ptcfast2

[alec_b]

Hitting a large enough bump may effect the feel because of the load being applied and removed from the bearing itself. If you're going in a straight line on a smooth road while the vibration is there, and you "swerve" the car back and forth, aka left-right motions, does the vibration change pitch/frequency at all?

[ptcfast2]

Hitting a large enough bump may effect the feel because of the load being applied and removed from the bearing itself. If you're going in a straight line on a smooth road while the vibration is there, and you "swerve" the car back and forth, aka left-right motions, does the vibration change pitch/frequency at all?

 

Yeah. The vibration lessens when I take the load off that side of the vehicle. Basically, when the car isn't going straight the vibration will dissipate enough to make a noticeable difference. The vibration is more pronounced in the floorboard than the steering wheel.

 

Seeing as this bearings seem more and more likely I've ordered 2 Timkin hub assemblies for the front wheels. I'll report back when I install them Thursday!

[ptcfast2]

Alright, so I installed the new bearing on the side with the vibration (driver) and all is well. The bearing's seal was starting to go on the bottom as it was all greasy/gunky. While I was under there I torqued everything I could get to to spec just to make sure nothing was loose and all seemed well.

 

Before driving off I decided to check the front end struts to make sure they were supporting the vehicle properly. The passenger side stabilized the car in 1 bounce and was pretty hard to press down. The driver strut stabilized the car in 2 1/2 bounces and was much easier to press down. It was also easy to bottom the strut out.......and it produced the clunk I've been hearing. It's the same clunk I would feel/hear occasionally when driving!

 

The strut is almost brand new, so I'm actually quite surprised it failed so quickly.

[ptcfast2]

Another update: The strut had failed, but it wasn't the cause of the vibration.

 

It turns out the vacuum line that goes from the plennium to the vacuum modulator on the transmission had cracked rubber connectors. The one connecting to the vacuum modulator even seemed to be collapsing on itself. Replaced them both and the car runs great. Vibration at the 65MPH+ mark is gone, RPMs are a bit lower at high speeds, shifting is smoother.