Thread: Vibration under load, cant figure it out.

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  1. #1 Vibration under load, cant figure it out. 
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    Hey guys, first post on what looks to be an awesome forum. Finally just bought an 02 GP GT. (Wanted one forever)
    I have one issue I cant figure out for the life of me. Car will run and drive fine cruising and accelerating normally. But if I really get on it above about 60 MPH I get this weird vibration that goes away when I let off. Sometimes feels like its in the rear, other times up front but i cant really tell. Any ideas? It has brand new tires that have been balanced twice cause thats what I thought it was. Gonna do a shakedown this weekend. Just looking for suggestions on what to look for as im new to these cars
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  2. #2 Re: Vibration under load, cant figure it out. 
    Killa Bee Scottydoggs's Avatar
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    axle and motor mounts need to be checked.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  3. #3 Re: Vibration under load, cant figure it out. 
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    Thanks for a quick reply! How would I go about checking the motor mounts? Just grab em and check for movement?
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  4. #4 Re: Vibration under load, cant figure it out. 
    Killa Bee Scottydoggs's Avatar
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    through the wheel well you can see them, the driver side is the trans mount, the pass side is the engine mount.

    the part with all that yellow crap on it is the engine mount, i filled it and made it a solid mount and smeared it over the top to help keep my oil leaks form killing it. as you can see its sits high. when shot they are flat.



    old and new side by side




    you can also hood open, car running, shift from P to r then to D then back to R. you want to watch the engines movement. if its moving back and fourth more then say 2 inches while changing gears the mounts are bad for sure.


    this was the mount that was in my car when i got it, when this bad the pass side of the engine will move and the whole engine will twist in the bay a full 2 inches back and fourth. odd it didnt clunk, or give me any vibrations.


    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  5. #5 Re: Vibration under load, cant figure it out. 
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    Awesome, Illcheck that out. How hard are they to replace?
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  6. #6 Re: Vibration under load, cant figure it out. 
    Killa Bee Scottydoggs's Avatar
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    http://www.grandprixforums.net/threa...nd-trans-mount not very hard.

    in his pics i dont see the board spanning the trans pan and oil pan. i use a 2x6 span both pans and jack the engine up. unbolting the dog bone mounts up top will let the engine raise up easier too.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  7. #7 Re: Vibration under load, cant figure it out. 
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    Im an idiot and forgot to check the mounts while I did my PS stuff. But ill do the gearshift thing when I have someone to help. Buuuuttt, I did my struts and I found that the sway bar linkage was pretty easy to move when it was off the strut. It also doesnt vibrate under 60 MPH. I can go WOT all the way to 60 no problem, but once it gets over 60 is when it starts. (pic of the sway bar linkage in question)
    2002 Grand Prix GT - no mods, probably gonna stay that way
    1997 Chevy K1500 - Flowmaster dual exhaust, 140 amp alt, blue LEDs err where, subs
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  8. #8 Re: Vibration under load, cant figure it out. 
    GT Level Member mainecrab's Avatar
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    I have dealt with odd vibrations up front for many things actually. Tires, tie rod ends, struts, wheel bearings. Last wheel bearing I replaced which I need to do again since newer one has a crappy ABS sensor it would shake a small bit at higher MPH like you are saying now. The bearing made no sound that would indicate a failure and only the ABS sensor having issues when hitting a bump like the other side did before it crapped out let me figure out the issue.

    In my experience the suspension on these vehicles needs to be replaced fairly often if you do not get really good parts, which is hard to tell what you are getting these days.

    So would check all the above things like mounts as well as suspension and steering parts for any issues like tie rod ends. If you never changed them take a look at both and make sure if you do replace them you do the inners too since they are a ***** to get out without the right tool rented and may as well save you some time by doing them both at once.
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  9. #9 Re: Vibration under load, cant figure it out. 
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    It doesnt seem like its coming from up front upon furhter experimentation. It almost in a way feels like ply separation in a tire. Checked tie rods, ball joints, and wheel bearings. Nothing is loose.
    2002 Grand Prix GT - no mods, probably gonna stay that way
    1997 Chevy K1500 - Flowmaster dual exhaust, 140 amp alt, blue LEDs err where, subs
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  10. #10 Re: Vibration under load, cant figure it out. 
    Killa Bee Scottydoggs's Avatar
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    rotate the tires then. see if it moves.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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