Hopefully someone has an answer to my problem. My 2000 ssei is shaking at highway speeds only. It is not terrible but definately noticeable. I got all the wheels rebalanced and did an alignment but it is still there.
I am not sure if this is related but when turning the steering wheel slightly back and forth in the center the steering wheel shakes a little bit. Very minimal but it just feels like something is loose in the steering column. Again, I am not sure if that is related, just throwing it out there.

Any ideas? Bad shocks possibly?

The "good" news is that your car is quite typical, and most of our Bonnevilles have the same problems. They are generally nuisance items, that will not cause any safety issues or breakdowns over time. The notorious "70mph death shake" has no known cure, but the clunky steering issue does:

viewtopic.php?f=55&t=217

If you do a search here in the forum you can learn more about the intermediate steering shaft issue.

If you do nothing to the steering, it will gradually get more clunky and annoying, but it will not "go out" on you.

These two items are basically design flaws in the car itself.

Ken_W

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2000 SSEi "Gypssei" - 206k miles - Light Bronzemist Metallic - stock
1999 Grand Am GT - 168k miles - Red - stock DEAD -- transmission died
2004 Pontiac Montana Ext 2WD - 207k miles - Blue Black Metallic - stock

What!?! your telling me that shake is normal? It must be something going bad, I can't imaging they did that from the factory.

It's not normal, however lots of 00+ Bonnevilles experience the same issues with vibrations.

There are lots of things it could be, and many members have replaced tons of parts to just have it remain.

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Bye Bye:

RIP sandrock

So far I have replaced wheel bearings, axles, inner and out tie rods, struts, shocks, regreased the intermediate shaft, new motor mounts and rebuilt the transmission all to have the vibration still remain.

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My former mistresses...2001 Bonneville SSEi...extensive mods...2007 Acura TL 3.2
And my new girl: 2008 BMW 535xi

Well you went that far so you might as well keep going right? Let us know when you figure it out.

I was reading a few other threads that suggest it might be aerodynamic? Can anyone confirm this? Does it go away when riding behind a semi?

That sounds exactly like my car.

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Inferno Red 2009 Dodge Caliber SRT-4 125k

New tires, factory and aftermarket wheels...
Mechanically, outside of the subframe, my car is entirely new. Alignment is perfect.

And considering the sheer number of people just living with this vibration, c'est la vie.

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My former mistresses...2001 Bonneville SSEi...extensive mods...2007 Acura TL 3.2
And my new girl: 2008 BMW 535xi

The only other thing it could be is the Lower control arm bushings, ZLTFUL.

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Bye Bye:

RIP sandrock

I have had all bushings all around replaced including lastly front lower control arms both sides. Now that being said I have to say that I noticed an improvement but the shimmy is still there. I suspect that the old bushing wore out from the constant shimmey only adding to the shake (I do a lot of hwy miles). Admitedly I have not replaced both rear lower control arms (they don't make just the bushing I believe - but could be wrong there. I rememeber giving up trying to find the bushings alone).

Incidently, I was the one who came up with the aerodymic theory. But trying the semi-trailer test might answer that question. I'll try that sometime.

The only other thing that is currently wrong with my car is my rear level is low - need to replace air ride leveling module. This seriously skews my camber? Anyway I didn't know until recently that I have been wearing out the inside edge of my rear tires. This maybe is connected to the shimmy - I'll find out soon as I now have a replacement module.

there's my two cents for now.

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Mark
The Familyman's Trans-Am
Intense 3.4 MPS, Intense FWI, Intense PCM, copper NGKs TR55's, MSD wires, MSD coils, BWD ICM, MagnaFlow High Flow Cat, drilled 180 'stat, solid front mount, Monroe Max Air rear shocks, Moog rear mounts, Moog suspension bushings, cleared front corners, 190,000 miles