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 Vibration / Shimmy at Cruising Speed

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seven
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PostSubject: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 1:56 pm

Hello everyone-I'm new to the site as I just picked up a 97 Riv S/C with 130k. My problem is I have a bad vibration that comes on at about 70mph. I have already had the tires balanced and put on new brakes front and rear with rotors turned. I do have a bad rear trans mount and wondering if that can cause this vibration. Anyone have a similiar problem? Just looking for advise.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 2:07 pm

Welcome. If the struts are original, I'd get them replaced. Also check tie rod ends and ball joints. I would think the bad mount could cause the problem if it happens under load. Does it shake when you're off the gas?

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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 2:08 pm

I've heard the vibration typically comes from: 1-trans mount or 2-harmonic balancer

if I had to guess, i'd say it's the mount.

Supposedly, there's a TSB saying adjusting the front? trans mount eliminates the common vibration.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 2:09 pm

was the wheel alignment checked??
i had a problem with my old car at about 70 mph when my steering alignment was off..
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seven
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 2:33 pm

It shakes on or off the gas. It's most noticable when cruising at 70, then accelerate hard for downshift to occur, then let off gas - really shakes then.
I don't know if struts have ever been replaced - i doubt it.
Ball joints look ok- I tried rocking the tires when jacked up looking for any suspension movement and they seem solid.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 4:23 pm

seven wrote:
Ball joints look ok- I tried rocking the tires when jacked up looking for any suspension movement and they seem solid.

The only real way to check ball joints is to unload them completely, meaning have the control arm supported "AND" the wheel off the ground, so there is no pressure at all on the BJ.
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Mr.Riviera
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 4:32 pm

is the vibration in the seat or the steering wheel? have any of the tires been filled with fix-a-flat? (probably not since they were able to balence the them but ya never know)

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seven
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 4:56 pm

The vibration is in both the seat and steering wheel.
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SoCal Riv
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 5:28 pm

Do you have the factory wheels installed, or are they aftermarket? If they are aftermarket do they require hub-centric rings? If aftermarket wheels, did they come with the Riviera when you purchased it? I ask this as you might not know that they require hub-centric rings. Were the front wheels taken off lately either by you or a shop prior to the shaking occurring?
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 5:32 pm

Rims are stock buick 16". I just bought the car a few weeks ago and it shook from the first time i had it at 70 mph. 1st thing I did was have the wheels balanced.
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Mr.Riviera
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 5:35 pm

any of the wheels have alot of weights on them? did the shop use rim lead or sticky lead? did you notice a difference after the balance? (better or worse)

if its done it since you bought it, them it's probably the tranny mount.

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seven
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Apr 24, 2007 7:05 pm

Standard rim weights used and nothing out of the ordinary in regard to the amount of weights used. There was no difference before/after.

I'm thinking rear trans mount because I can even feel "movement" under part throttle shifts
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Sat Jul 07, 2007 7:51 am

Dragging up an old thread here, but I'm experiencing a similar vibration. In fact it just seemed to happen on the way to work last night - I even pulled over because I thought I had a flat tire! My wheels and tires haven't been touched for months, so there were no recent changes. I noticed that there are no weights on either right side wheel (at least on the outward facing part of the wheel) and thought it was possible that a weight fell off, but that seems unlikely to happen to two wheels, so they probably balanced them without a weight (I never really looked before).

I may take a wheel off this morning and check out some suspension components. Otherwise, another test will be the replacement of my wheels and tires (which I had planned anyway) - probably on Monday. But I'm glad to see this thread to give me some ideas. Thanks guys!
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Sat Jul 07, 2007 10:39 am

check for a broken belt in the tire..hit any pot holes lately?? while its vibrating..put the trans into nuetral..to take it out of the equation...
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Brad95Riv
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Sat Jul 07, 2007 1:31 pm

Well, haven't had a chance to test it since taking a look, but....I did notice that several of the lugnuts on the front left tire were loose! And that would be my own fault - I replaced the wheel bearing a few months back, and I never retorqued the nuts after driving for a while. That's never been a problem for me before, but I'm sure the situation this time was a little different. I put brand new lugnuts on at the time (several of the old ones were damaged in trying to get the old bearing off - that's a whole other story). Plus the studs and the bearing were brand new, so I'm guessing that everything just kind of stretched and vibrated a bit, causing those lugnuts to get loose.

Right now, I'm assuming that was the cause of my vibration, but I'll check it out tonight. I should be replacing my wheels and tires on Monday, so when I take my current wheels off, I'll check that one to see how tight the lugnuts are then. Or...maybe I should check the lugnuts tomorrow morning after work...
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Mon Jul 16, 2007 6:54 pm

Just like to through in my experience hoping someone can take something from it. I have the same vibration at about 70mph, but one thing I've noticed, which I don't know if it's related or not is that when I start the car, in park, it idles smooth. As soon I pop it into drive or reverse it starts to tremble a little, so I'm thinking (from my limited automotive repair experience) that it may have something to do with a transmission mount that needs to be replaced. I haven't had time to take a closer look at it, but as soon as I can get my hands on a manual for my 97, I'll do just that.
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seven
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Jul 17, 2007 1:56 pm

I've looked into many possibilities and still stumped. For my 97 Riv, the problem is not tires or wheels. I took all 4 tires/wheels off my fathers 99 Park Avenue and put them on the riv and the problem is still there. It is slowly getting worse. It starts now at about 63mph. When cruising at say 70 it is vibrating -sometimes bad and sometimes not so bad, but now when I let off the gas at that speed it vibrates even worse. I have changed my bad rear trans mount and there is no difference.
I've had it to 2 shops and both said all front end parts are tight and no problems. One said the only thing he can think is it is internal in the trans.
Now with the trans, only thing I notice is under very light load, at times it shifts smooth, other times it really clunks into 3rd and 4th.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Jul 17, 2007 3:08 pm

harmonic balancer problem? sounds like its only vibrating around 2krpm when it is in OD, maybe tranny related. i wish i could help frown

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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Jul 17, 2007 5:09 pm

Im finding that im having the same problem between 45 and 50 mph. The tranny seems to up and downshift a few times shaking the car, and then i feel a shake through the steering wheel like there's some sort of axle hop. Is this the same problem as everyone elses? should i check the struts and trans mounts?
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Wed Jul 18, 2007 10:47 pm

My '98 had a problem with 'radial force variation' in the tires. See Wikipedia (http://en.wikipedia.org/wiki/Radial_Force_Variation) or Tire Rack (http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=17)for a more detailed explanation.

My problem was solved when I had a cadillac dealer remount the tires with a Hunter 9700 balancer. Point is that the Hunter not only does the balancing, but also measures eccentricity in the rim and tire (to match lo spot in rim with stiffest part of tire). I assume there are other machines that do this, but the Hunter is the only one I know of. Reason I mention cadillac dealer is that I was told once by a service manager that the caddy dealers have to have one or to know where to find one. Won't go into detail here - I'm not sure

Some tires (notably Michelins) don't have all that much radial force variation, in my experience. Some do. And I was once told (and it's also in the Wikipedia article) that some manufacturers ship low-spec tires to less sensitive markets (like the one I live in, in rural New York).

Another source of vibration would be problems (deep rust, warpage or mosmounting) of brake rotors, although they don't necessarily and don't consistently cause a pulsation at speed that some call a vibration. Depends on how close the pads sit to the rotors after stopping and how bad the rotors are warped.

Best of luck solving your problem.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Thu Jul 19, 2007 7:38 am

My riv does a little of that vibration. It happens around 70 and i come out of it when turning right (slightly ofcourse, i mean i am going 70+)
But it doesn't stay shaking. I'm sure it's a steering problem.

Have you tried putting it in a dyno and inspecting it?
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Fri Jul 20, 2007 5:25 pm

Mr. Riviera -- It vibrates the same independent of RPM. It dosen't matter if it's in 2nd, 3rd, or 4th, at 70 mph it vibrates. This would rule out harmonic balancer. Also not load dependent as it still vibrates if I slide it into neutral.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Sat Dec 01, 2007 11:25 pm

This isn't gonna help probably but I just put brand new tires on and my vibration is gone. I was getting it about 65 and worse at 70... and going down hills for some reason made it worse!
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PostSubject: chasing the 70 mph shimmy   Thu Feb 07, 2008 11:04 am

I went to an alignment shop for analysis. He told me that I needed inner tie rods and a right front hub. Having never been to this guy before, I left it in the hands of a long time friend who owns a body shop. He told me that nothing was wrong.

He turned the rotors and installed monroes on the rear. I installed monroe front struts within the last 30,000 miles or two years. Front feels great. he also performed an alignment.

Shimmy was still there and seems speed related. Shifting into neutral the intensity remains steady. Intensity seems to vary and occurence isnt easy to predict. Ususally around 70 and sometimes comes and goes on cruise control.

Yesterday, I installed new tires. Tech said that the wheels and tires balanced out as good as any he has seen. I had them do a visual on the motor and tranny mounts. They did not see anything.

I also changed the tranny fluid and added lucas.

I drove the car 70 miles last night and the shimmy is still there, although greatly reduced.

One other clue may be the cars temp getting up to the red zone on idle and climbing steep grades. This is new.

Do you guys think that a water pump could be causing all of this?

Other ideas are a harmonic balancer and tranny/motor mount issue not visually noticable.

Help me hang onto my owned since new 98. I'm not willing to invest a whole lot more time or money. Any ideas?
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Thu Feb 07, 2008 11:11 am

I don't think the higher engine temp has anything to do with your shimmy. I used to have a vibration that came and went, but it has diminished since I started replacing shocks/struts, and other suspension parts.

If it's speed related, does it only happen on acceleration? Is is very pronounced, or only slight? Is the vibration visible in your steering wheel?

Have you replaced the rear shocks recently?

_________________
'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


'05 GTO 49k miles 0-60: 4.8s 16.9 avg MPG Nelson Ledges Lap: 1:26
Because fun
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