LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Vibration issue... I need some input...

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Old Apr 23, 2007 | 10:03 AM
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Default Vibration issue... I need some input...

the car only vibrates hard from 70-80 at WOT or when accelerating very quickly (rattles the change in my console pretty bad)...
If i am chugging along between 70-80 the car is fine...(no vibration felt)
The wierd thing is that i went from 3:73's to 3:42's and the vibration stayed consistant at 70-80...

would low gear oil do this? because my rear is leaking pretty bad... (from the front and rear)...

i have replaced: rear rotors, driveshaft, set the pinion angle, transmission, damper pulley, rearends, u-joints, spindles, front rotors, hubs, mounts, had the wheels balanced... i pretty much did everything and i still have this GD vibration...

i'm running out of ideas... and i'm wondering if bad springs could cause this? i am frustrated and clueless...

can someone either help me or refer me to a drivetrain specialist... (in the SW PA area)

thank you
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Old Apr 23, 2007 | 03:02 PM
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Check your tires for flat spots.
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Old Apr 23, 2007 | 03:14 PM
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i have a similar problem. it started after i got a new tranny. mine has a terrible vibration in overdrive at about 110mph. could it be an off balanced drive shaft? did your vibration start AFTER u replaced something?
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Old Apr 23, 2007 | 03:35 PM
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If you changed the gear ratio and it still vibrates at the same mph, I would put my money on a bad tire or axle.
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Old Apr 23, 2007 | 06:30 PM
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Originally Posted by Razor_Blade
If you changed the gear ratio and it still vibrates at the same mph, I would put my money on a bad tire or axle.

i changed the whole rearend and housing...
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Old Apr 23, 2007 | 07:29 PM
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Originally Posted by LTBANDIT
i changed the whole rearend and housing...

Have you tried some different tires? Find someone with a similar size wheel & tire combo and talk them into letting you swap them out for a test drive.
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Old Apr 23, 2007 | 07:51 PM
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Originally Posted by Razor_Blade
Have you tried some different tires? Find someone with a similar size wheel & tire combo and talk them into letting you swap them out for a test drive.

yup, i have c5 wheels and tire that i tried and the vibration is still there...

it is def. speed sensitive and not rpm sensitive...
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Old Apr 23, 2007 | 07:59 PM
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Get a LS1 Aluminum Driveshaft, and it will disappear..
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Old Apr 23, 2007 | 08:45 PM
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Originally Posted by the_merv
Get a LS1 Aluminum Driveshaft, and it will disappear..

you might not believe this... but, i tried it, sold it, and bought an inland aluminum ds...
still vibrates...

i must have the incurable vibration problem...

i spoke to a guy who has a dyno and we will put the car on it and see if he can find anything...
he said he should be able to pinpoint it...

til then i am open to suggestions...
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Old Apr 23, 2007 | 09:59 PM
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I'm telling you it's the driveshaft, I know you replaced it, but the one you got might not be balanced.
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Old Apr 23, 2007 | 09:59 PM
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I'd like to know what it was though.
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Old Apr 23, 2007 | 10:02 PM
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do you have poly motor mounts and/or trans mounts???? i have the same issue, changed, tires, wheels, tq arm, rebalanced stock, then repalced with LS1, replaced axles, then whole rear end, then tranny sitlll there...i have nothing more to repalce..still vibrates...
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Old Apr 23, 2007 | 11:01 PM
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^^Team America Avatar, that's great..

Might have thrown the weight off of the Flex Plate. Chances slim to none, but you never know. Balancer could be coming apart also..
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Old Apr 24, 2007 | 01:43 AM
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Originally Posted by the_merv
^^Team America Avatar, that's great..

Might have thrown the weight off of the Flex Plate. Chances slim to none, but you never know. Balancer could be coming apart also..
That would be RPM sensitive.

If it started after the rear end swap, it could be numerous things. Re-tighten every bolt back there, put in new U-joints. If still, replace the rear rotors. If still, replace the axles. If still, ring and pinion, and still, then the carrier. I assume you still have you old one to pull stuff of off to swap in, like the rotors at least?
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Old Apr 24, 2007 | 06:11 AM
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Originally Posted by Formula350
That would be RPM sensitive.

If it started after the rear end swap, it could be numerous things. Re-tighten every bolt back there, put in new U-joints. If still, replace the rear rotors. If still, replace the axles. If still, ring and pinion, and still, then the carrier. I assume you still have you old one to pull stuff of off to swap in, like the rotors at least?

if you go back to my initial post you'll see that i replaced everything... it vibrated the same before and the same after... some things have been replaced twice...

i need to look at things that i did not replace... but the cheapest and easiest would be to get the tires checked for flat spots and spun balanced...
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Old Apr 24, 2007 | 06:12 AM
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Originally Posted by 94/96ZsM6s
do you have poly motor mounts and/or trans mounts???? i have the same issue, changed, tires, wheels, tq arm, rebalanced stock, then repalced with LS1, replaced axles, then whole rear end, then tranny sitlll there...i have nothing more to repalce..still vibrates...

i have poly motor mounts... but it vibrated before also...

now i did have the poly trans mount... however, the poly mount vibrated from 30-40 so i replaced it with the ls1 mount and that vibration is gone...
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Old Apr 25, 2007 | 09:18 PM
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i've thought about replacing the poly trans mount with a rubber ls1 to see if it makres a difference. at this point i have given up and will drive it the way it is. there is nothing to replace,besides the trans mount, so i will have to live with it.
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Old Apr 25, 2007 | 09:22 PM
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did you check the bushing inside the tailhousing?
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Old Apr 25, 2007 | 10:51 PM
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Replaced the rear shocks? Hows the panhard bar bushings? Front tie-rods?
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