Thread: Shaking at 45-55mp?

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  1. #1 Shaking at 45-55mp? 
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    Hey gang.

    Back to my son's 2001 Grand Prix GT with the 3800 motor.

    He's got a "shaking" that feels like the motor, not suspension/front end, that starts around 45mph,
    then lasts until 55mph or so, where it smooths back out.

    When I say shaking, I mean far more than just a shimmy - its a very pronounced shake.

    So far, we replaced:

    front sway bar (it was broke)
    both motor mounts (trans mount was completely blown out, other one actually was in pretty good shape - replaced
    both anyway)
    right and left tie rod ends
    top torque strut - it was broke
    4 new tires
    front end and rear end alignment

    However, the shaking still continues.

    Anyone have any other ideas as to what it might be? We've kind of run out of ideas here.

    Thanks!
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  2. #2 Re: Shaking at 45-55mp? 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    You can try to rotate the tires and see if it stops. Might be a seperated tire.

    Otherwise I'd prolly look at an axle issue.

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  3. #3 Re: Shaking at 45-55mp? 
    Killa Bee Scottydoggs's Avatar
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    did you have the tires balanced? if not try to rotate them.

    if the tires are low on threads, they could just be warped and you need new tires. seen more then one set of tires wear out and bounce.

    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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  4. #4 Re: Shaking at 45-55mp? 
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    Hmm, sorry if I didn't make that first post quite clear...

    We've already put 4 brand new tires (Goodyear Viva's) on the car, balanced, and front and back end alignments done

    Didn't help.

    Thanks!
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  5. #5 Re: Shaking at 45-55mp? 
    Killa Bee Scottydoggs's Avatar
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    did you check out the lower control arms yet, or the struts? do they pass the 3 bounce test? you push down on the fender and the car should stop moving with in 3 bounces.


    heres a diy for lca's. has pics of bad ones. http://www.grandprixforums.net/how-c...rms-66203.html

    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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  6. #6 Re: Shaking at 45-55mp? 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    I found the problem, its those goodyears.......

    But anyway, try to rotate them. I know you just bought em, but see if it helps any, could be a tire problem.

    Otherwise like I said before, might be an axle problem. I cant be certain though.

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  7. #7 Re: Shaking at 45-55mp? 
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    Quote Originally Posted by Fivefingerdeathpunch View Post
    I found the problem, its those goodyears.......

    But anyway, try to rotate them. I know you just bought em, but see if it helps any, could be a tire problem.

    Otherwise like I said before, might be an axle problem. I cant be certain though.
    Well, the problem existed *before* we put the 4 brand new tires on. We changed the tires
    hoping it would fix it, and it didn't so....

    Guess we'll look at the LCA's, struts, and the axles next.

    Thanks all.
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  8. #8 Re: Shaking at 45-55mp? 
    SE Level Member destroyer85golf's Avatar
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    it sounds like a half shaft problem.
    2000 GTP daytona 500
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  9. #9 Re: Shaking at 45-55mp? 
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    Woohoo, good news to report!

    My son and I finally got our work schedules co-ordinated and the weather co-operated (nice, sunny 70 deg day here in Eastern Kentucky - aside from the highly unusual 4.3 mag. earthquake), so we picked up a set of half axles and replaced the ones in his 2001 Grand Prix. Honestly, the one on drivers side was probably okay, but the one on the passengers side definitely had problems. Everything went fairly smooth, up until we got to the passengers side, ready to insert the new half shaft. That's when we noticed the output seal. Pretty battered, so we decided to go ahead and change. I mean, what's 5.49 after all the work and money getting there? I had a seal removal tool (one of those little tools that looks like a small ice pick) and it worked pretty good. Our problem was getting the new seal back in place. We had a 36mm socket for the old axle nuts, but that wasn't big enough to cover the seal right, so that we could tap it in straight and even. We finally used a flat-ended crowbar on one side, my son holding that, while I tapped it 180 degrees from that point. Took some doing but we got it in.

    To sum it up, he took it out for a test drive, came back with a big sloppy smile on his face. Problem solved, he says it rides smoother than a baby's bottom now.

    Thanks to everyone here for all the suggestions and the guides I found in the forums.

    2 thumbs way up!
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