Chassis/cabin vibration at highway speeds only

[Mozza1219]

Update!

So I went all out today and changed the following:
1. CV boots
2. Rear subframe bushings
3. Rear trailing arm bushings
4. Rear wheel bearings

took the car for a drive afterwards and my vibration is complete gone!

I personally suspect it was a bad rear wheel bearing (driver side), it just didn't sound quite right when I was spinning it by hand. Again, this did not transmit into any noise in the cabin, but instead I think it was the cause of my vibration.

The reason I do not think it was the subframe or rear trailing arm bushings was because when I pulled them out, they didn't look like they were in that bad of a condition. For example, the subframe bushing came out all in one piece.

Hope this helps anyone who may have the same symptoms as myself. It was busy 2 days, but I'm so happy I got my car finally sorted.

Cheers all! Happy to take any questions about dropping the subframe or doing the rear wheel bearings as it's all fresh in mind.

[twright]

You're testing with 1 bad wheel won't tell you much if you have two bad ones on the car. It will still shake. Get 4 good wheels on the car and see where you are. Wheels can be straightened. It usually costs about $100 a wheel.

Bad wheel bearings make noise. I haven't seen one cause a vibration problem unless its so bad that the balls have all fallen out of the bearing.

I've changed a lot of bad bushings. None of them caused a vibration problem. You can tell they're bad because of handling problems.

[Mozza1219]

Have you checked the wheels for straightness?

If you have and they're OK, change your Front Control Arm Bushings. These can be bad and look fine. The good news is that they are cheap.

I took a closer look at the wheels and yes, one wheel is definitely in worse shape than the rest. The other 3 are ok, with the exception of 1 which also has a slight warp in it. So that makes 1 bad wheel and 1 sort of bad wheel right?

So I got my spare wheel from the boot and went through each wheel, swapping it out one by one. The spare is in perfect condition and the tyre seems ok.

The vibration was exactly the same on each drive. I get why it would seem like a bent wheel is causing this, but after swapping each wheel out individually I don't think this is the issue.

I've already swapped the front control arm bushings out.

I'm leaning towards a bad rear wheel bearing, rear trailing arm bushings or subframe bushings. But I havnt summoned the will power to drop the subframe and replace the bushings yet...

[Mozza1219]

If you want to get precise on driveline angle, start checking it and see if something is off: https://www.moderndriveline.com/driveline-angle-finder/ It can tell you is the engine/trans mounts or the rear diff is out of what in relationship to one another. If they are spot on or very close, then its either driveshaft balance. You mentioned that the driveshaft has new joints. Was it balanced after that?

I'll have to look into this link, so it's like an app or something.

Correct, driveshaft was balanced when the UNIs were replaced.
Even after putting the reconditioned driveshaft in, the car drove fine and maybe a week or two after the vibration started.

[twright]

Have you checked the wheels for straightness?

If you have and they're OK, change your Front Control Arm Bushings. These can be bad and look fine. The good news is that they are cheap.

[jbontke]

If you want to get precise on driveline angle, start checking it and see if something is off: https://www.moderndriveline.com/driveline-angle-finder/ It can tell you is the engine/trans mounts or the rear diff is out of what in relationship to one another. If they are spot on or very close, then its either driveshaft balance. You mentioned that the driveshaft has new joints. Was it balanced after that?

[Mozza1219]

I cased a similar vibration at 75-80 for a year. It went away when replaced the engine and trans mounts. Drive line angle is important.

Trans mounts replaced. Not sure that it can be engine mounts seeing as it is only speed sensitive.

I still haven't figured this one out and I've just been dealing with the vibration, but it does get on my nerves and gets in the way of me really enjoying the car.

I had the car on jack stands (under the trailing arms so there was some weight on the springs) and ran it up to speed. Vibration was still there and felt exactly the same. I don't know if I'm game to run the car with the stands on the subframe, I heard you shouldn't put the CVs at that angle and run the car? Let me know if I'm wrong about this.

[jbontke]

I cased a similar vibration at 75-80 for a year. It went away when replaced the engine and trans mounts. Drive line angle is important.

[Mozza1219]

I'd suspect something went wrong with the driveshaft remanufacture.
Check the caps on the joints to see if they all protrude from the yokes the
same amount, then see if there are any shiny spots where a weight might have
flung off.

You can stick a little camera and a light down there, and see what it's doing at speed.

I've had numerous driveshaft vibes, and yes, the cabin resonates in a way that
you start to recognize after a while.

hth

t

Thanks TobyB.

I did have a look to see if any weights had come off and everything looked ok there, but I didnt check the caps. Even if everything looks ok, would you suggest taking the driveshaft off and bringing it back so they can check the balance?

[TobyB]

I'd suspect something went wrong with the driveshaft remanufacture.
Check the caps on the joints to see if they all protrude from the yokes the
same amount, then see if there are any shiny spots where a weight might have
flung off.

You can stick a little camera and a light down there, and see what it's doing at speed.

I've had numerous driveshaft vibes, and yes, the cabin resonates in a way that
you start to recognize after a while.

hth

t

[twright]

Thanks twright.

I'll try and get my hands on a set of different wheels and see if it's any better.

But since I swapped the wheels from front to back, if a bent wheel was the culprit, wouldn't the vibration move into the steering wheel?

Not if you have two bent wheels.


Jack up the car and spin the wheels. It's the only way to know if they are straight, and it doesn't take very long to do.

[Mozza1219]

You need to find out if your wheels are bent. Just because two different shops balanced them, it doesn't mean that they might not be bent. (you can balance an egg, but it won't roll very well)

The way I check wheels is too jack up each wheel and spin them by hand. If they are really bent, you can see it right away. If they are only bent a little bit (1/16" is too much), you have to place something on the ground next to the rim (scissors jack?) so you can see if the wheel moves in relation to your reference point (scissors jack).

You can chase vibration problems forever with a bent wheel. Those have to be straight. Don't let the tire guys tell you to just put them on the rear. That won't work if you want it smooth.

Thanks twright.

I'll try and get my hands on a set of different wheels and see if it's any better.

But since I swapped the wheels from front to back, if a bent wheel was the culprit, wouldn't the vibration move into the steering wheel?

[twright]

You need to find out if your wheels are bent. Just because two different shops balanced them, it doesn't mean that they might not be bent. (you can balance an egg, but it won't roll very well)

The way I check wheels is too jack up each wheel and spin them by hand. If they are really bent, you can see it right away. If they are only bent a little bit (1/16" is too much), you have to place something on the ground next to the rim (scissors jack?) so you can see if the wheel moves in relation to your reference point (scissors jack).

You can chase vibration problems forever with a bent wheel. Those have to be straight. Don't let the tire guys tell you to just put them on the rear. That won't work if you want it smooth.

[Mozza1219]

Long shot, but let's assume you have a bad rear tire. One way to eliminate that would be to swap rears with fronts and see if the vibration comes to the steering ?

I think i've already swapped the wheels around but i can't remember so I'm going to try that today. Also going to try and back the handbrake off a little more as I recently replaced the shoes and didn't really understand how tight it was. I'll report back with my findings.

Interestingly, the vibration has changed a bit, the range at which it vibrates is now bigger, it seems to vibrate beyond 70mph, but the frequency of the vibration is at its worst at 60mph, which is why its more noticeable at that speed.

UPDATE: swapped the wheels from front to back, no change.

[Westija]

Long shot, but let's assume you have a bad rear tire. One way to eliminate that would be to swap rears with fronts and see if the vibration comes to the steering ?