Thread: shudder under acceleration

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  1. #1 shudder under acceleration 
    GT Level Member nicks98gtp's Avatar
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    first off if this is in the wrong section please move, not sure where this would fall. But now to the problem, ill explain as best i can, when im under light/moderate acceleration i can feel a shudder throughout the car (mainly right after the 2-3 shift when the rpms are really low) but its throughout the whole powerband. I did notice that the dogbone mounts and motor mount over the radiator do have a lot of play and they look cracked. I was wondering if the shuddering could be a result of those mounts being/going bad? also when the car is first stvrted it will go into lockup fine while crusing, but after the car gets to operating temp and im cruising it will pop out of lockup. it shifts through all four gears fine, but just no lockup unless i restart the car. ive heard that they will pop out if knock is detected? can anyone put any truth to that? and my thinking is the shuddering might be registering as false knock. the shudder/vibration gets worse when the wheel is turned to the right if that helps also. thanks for reading my novel guys and any input is appreciated.
    98 Gtp, ported s/c, fully rebuilt motor .20 oversized pistons, rebuilt trans, zzp pcm,more mods to come
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  2. #2 Re: shudder under acceleration 
    Moderator dsmuts's Avatar
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    Does it have all stock suspension?
    98 GTP modded 1.9's, sd headers, 3.4", zzp 1.0 230K miles scrapped.
    04 Comp G zzp stb's, UMI ta's, Speedbuilt sways, bully flo heads, XP, zzp headers, fsic, thrasher shift kit, 60#, 2.6" corsa 2.5", Inferno hood
    01 gt z7 turbo tep trans zzp motor
    08 g8 gt cam exhaust 11.87@118
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  3. #3 Re: shudder under acceleration 
    GT Level Member nicks98gtp's Avatar
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    its got replacement autozone struts and moutns in the front with stock springs. and gabriel ready mount struts int he rear. other than that all stock
    98 Gtp, ported s/c, fully rebuilt motor .20 oversized pistons, rebuilt trans, zzp pcm,more mods to come
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  4. #4 Re: shudder under acceleration 
    Moderator dsmuts's Avatar
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    jack up the front end and see if anything looks or moves out of the ordinary. It might be some worn suspension parts.
    98 GTP modded 1.9's, sd headers, 3.4", zzp 1.0 230K miles scrapped.
    04 Comp G zzp stb's, UMI ta's, Speedbuilt sways, bully flo heads, XP, zzp headers, fsic, thrasher shift kit, 60#, 2.6" corsa 2.5", Inferno hood
    01 gt z7 turbo tep trans zzp motor
    08 g8 gt cam exhaust 11.87@118
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  5. #5 Re: shudder under acceleration 
    GT Level Member nicks98gtp's Avatar
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    only other things i was thinking would be the passenger axle (driver has been replaced) along with both control arms, both side tie rods. bottom motor mount and trans mount look good. all the parts are stock gm parts, and have less than 15k miles on them besides the axle. would the dog bones cause a vibration like that do you think?
    98 Gtp, ported s/c, fully rebuilt motor .20 oversized pistons, rebuilt trans, zzp pcm,more mods to come
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  6. #6 Re: shudder under acceleration 
    Moderator dsmuts's Avatar
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    i wouldn't think they would cause that bad of a vibration but i've never had any go bad on my so i really don't know. Try flipping your dog bones and see if it helps.
    98 GTP modded 1.9's, sd headers, 3.4", zzp 1.0 230K miles scrapped.
    04 Comp G zzp stb's, UMI ta's, Speedbuilt sways, bully flo heads, XP, zzp headers, fsic, thrasher shift kit, 60#, 2.6" corsa 2.5", Inferno hood
    01 gt z7 turbo tep trans zzp motor
    08 g8 gt cam exhaust 11.87@118
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  7. #7 Re: shudder under acceleration 
    GT Level Member nicks98gtp's Avatar
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    thats what i think may have did it, i flipped them in the summer and they stuck like a bi*ch even with wd40 and both are ripped on the (now) top front and bottom sides facint the motor. when i hold the ake and gas it you can see them move a good little bit
    98 Gtp, ported s/c, fully rebuilt motor .20 oversized pistons, rebuilt trans, zzp pcm,more mods to come
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