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CMQ
User
Oct 1, 2013, 4:24 PM
Post #1 of 7
(1945 views)
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1994 Bonneville shaking
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I have a 1994 Pontiac Bonneville with around 208,000 miles for a work car. A couple months ago it started shaking pretty bad from 40mph on up. It had a bad tire on the back with the belts coming through. I bought two new tires and had them put on the front and rotated two of the other ones to the back. Still didn't fix the problem. The shop I took it to said the back tires were pretty out of round so they rebalanced them. Still didn't fix the shake. I bought two more new tires and had them put in the back. It drove smooth for the first 30 miles or so and the shake came back. Sometimes there's hardly any shake to it, sometimes a little, and sometimes it feels like the tires are going to fly off the car. I can't feel the shake in the steering wheel but can definitely feel it under my seat when it does. To me it feels like it's something to do with the back end. I've poked my head under a couple different times and checked everything out. Nothing seems to be broken or missing, but I'm no car mechanic by any means. I had a friend of mine say maybe a wheel bearing. But I'm not sure on that either. Any advice on what to look for or tricks to identify the problem would be appreciated. Hopefully it's nothing too serious. I'd like to keep driving it for work but don't want to stick a bunch of money in it.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 1, 2013, 4:47 PM
Post #2 of 7
(1935 views)
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Re: 1994 Bonneville shaking
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Hmmm? You said you are not a mechanic so I take that, that you will be seeking help from a shop.
Something is wrong putting new tires on a bad rim(s) and tire places should be looking for that. You could have just a couple bad wheels. I'm getting tired to look it up but this probably has a hub for back wheel bearings non serviceable and if they are so or just one so bad you can get shaking out of them it's plain dangerous.
Any decent tech should be able to just lift each back wheel and spin them and feel for a bad bearing. No free play allowed.
There are other things that could cause shaking or an out of balance feel but you said it was noticed already and had an out-of round wheel balanced which achieves nothing if wheel and tires aren't true. You can balance a square for that matter.
Have to suggest getting this looked at by perhaps another place or tech to be safe and save new tires from wearing into a wheel problem if so,
T
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CMQ
User
Oct 2, 2013, 8:17 AM
Post #3 of 7
(1904 views)
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Re: 1994 Bonneville shaking
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I also forgot to mention it only shakes when I'm accelerating or have my foot on the pedal. If I let off and coast the shake is non-existent and if the cruise is on (very rarely use it) it doesn't shake except for hills and very minor shaking. The shaking also stops around 70mph on up. But the speed limit is 65mph so going 70 or over isn't really in my best interest and really not the speed I want to be going if it is something dangerous that's wrong. I'm not sure if this little bit of info would change any diagnosis.
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Hammer Time
Ultimate Carjunky
/ Moderator
Oct 2, 2013, 8:53 AM
Post #4 of 7
(1900 views)
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Re: 1994 Bonneville shaking
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That sounds like a bad inner C/V joint.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 2, 2013, 9:04 AM
Post #5 of 7
(1899 views)
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Re: 1994 Bonneville shaking
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Let's start over. This is now a load on engine/drivetrain issue more than likely not wheels or tires themselves. I was thrown off by you saying a rear tire was all screwed up and if not true it really or any of them wouldn't be exacerbated by load.
So now I suggest you check for motor mounts including transmission and all involved to hold engine in place which is rubber mounted so you don't feel it much
AND so it doesn't move to far as a unit.
That torque on engine is probably the source with FWD it's also stressing the exhaust system which must tolerate some forward backward tilting of motor.
You said you are NOT a mechanic so don't do or try anything you don't fully understand and can absolutely do safely!
You can just open hood and likely have a view of top parts of engine from driver's seat. This would be step one if alone. Just hold brake firmly, nothing around in front or rear of vehicle at all. Apply some power with gas pedal watching engine move in both forward and reverse. It will move some but not too much and you probably wouldn't know off hand but might feel it when you let go of power to gas pedal. DO NOT OVERDO IT!
Next requires someone else to do that while another watches the mounts - never stand in front of a vehicle for that trick!!!!
This should be quick and easy for a tech to just do while you wait to at least rule it out or point out that they are bad. If and repeat IF this is the issue it wouldn't be noticed just idling or no load on engine in most cases. If mounts to subframe which are rubber also are all rusted out or visible issues it could be a real problem.
This could still be something else completely but now with your description is the most likely are for the problem,
T
(edit) HT is right also. Could be a CV joint, inner as outer ones would show when steering more likely)
(This post was edited by Tom Greenleaf on Oct 2, 2013, 9:06 AM)
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CMQ
User
Oct 9, 2013, 8:38 AM
Post #6 of 7
(1867 views)
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Re: 1994 Bonneville shaking
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Turns out it was a bad cv joint. Had both replaced a few days ago. Rides like a Cadillac now. Except now the motor seems to sputter. While I'm accelerating it will cut out a little bit and the tach will bounce up and down a bit. It shifts fine and all of the other gauges are fine. It seems to run perfectly fine when it's cold in the morning but once I drive 10-15 miles it starts doing the cutting out. I can't remember for sure but I had an O2 censor replaced a few years ago and it seems like this is similar to that. Or maybe bad plugs or catalytic converter or maybe I'm completely off on all guesses?
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Hammer Time
Ultimate Carjunky
/ Moderator
Oct 9, 2013, 9:51 AM
Post #7 of 7
(1864 views)
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Re: 1994 Bonneville shaking
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Closing this question as solved.
If you need help with other issues, then start a new question for that please
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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