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

Vibration in Driveline

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Old Oct 28, 2009 | 11:20 PM
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Default Vibration in Driveline

Ok, so I just finished the 383 build and got everything in the car. I am taking the car tomorrow to get it aligned because I put a tubular K member in the car.

When the car is sitting still (it still hasn't seen the road yet) anything higher than 2000 RPMs the driveline starts vibrating. I can feel it in the WHOLE car, the seat, shifter, floorboard, EVERYTHING.

The rotating assembly was balanced by a reputable shop and nothing else was changed. Still running the same tranny, flywheel, pressure plate, clutch, balancer EVERYTHING.

Any help would be appreciated guys.
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Old Oct 28, 2009 | 11:30 PM
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One thing to check is your U-joints. Make sure its seated all the way and in good condition. I would also check to see if any of the needles fell out and if the drive shaft is bolted down tight.
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Old Oct 28, 2009 | 11:33 PM
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98 % sure the ds is bolted down right. but i can check that in the morning.

Anyone else?
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Old Oct 28, 2009 | 11:34 PM
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Originally Posted by LT1
One thing to check is your U-joints. Make sure its seated all the way and in good condition. I would also check to see if any of the needles fell out and if the drive shaft is bolted down tight.
He said it does it with the car not moving so it's not the driveshaft/ujoints. It has to be something in front of the trans.

If the flywheel you have was setup for factory bottom end style balancing (with a weight in the flywheel) but they "zero balanced" the new rotating assembly, that would be your problem.
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Old Oct 28, 2009 | 11:37 PM
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OHhh ok sorry i missed that

Thats true car has to be moving for it to be anything to do with the drive shaft. Unless he had the rear up on jacks spinning it.
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Old Oct 29, 2009 | 12:23 AM
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Originally Posted by Purple95Z28
He said it does it with the car not moving so it's not the driveshaft/ujoints. It has to be something in front of the trans.

If the flywheel you have was setup for factory bottom end style balancing (with a weight in the flywheel) but they "zero balanced" the new rotating assembly, that would be your problem.
The flywheel was balanced with the rotating assembly.
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Old Oct 29, 2009 | 12:24 AM
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I believe the Flywheels and Flexplates are neutral balanced from the Factory..

From the sound of it you may have a misfire..
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Old Oct 29, 2009 | 12:29 AM
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Originally Posted by the_merv
I believe the Flywheels and Flexplates are neutral balanced from the Factory..

From the sound of it you may have a misfire..
They aren't neutral balanced from the factory.. LS1s are but LT1s have weighted flywheels/flex plates.

You're totally right though, if it's not a balance issue it's a misfire. 100% sure you have the plug wires on the right opti terminals? 100% sure all plug wires are on the plugs and opti terminals fully? Just basic things to check that get overlooked sometimes.
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Old Oct 29, 2009 | 12:32 AM
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Ah..ok.. I knew my LS stuff is all neutral.

Ya the only thing that explains his problem is a misfire, that's the only thing that is left..
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Old Oct 29, 2009 | 01:27 AM
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the way it was, it was a STEADY shake, constant, there was no intermittancy to it. Also, no popping/etc like with a miss. Just feels like a washmachine throughout the car
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Old Oct 29, 2009 | 03:33 AM
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does the shake vary with rpm? I am also leaning towards the pulg wire issue as I have made this mistake myself at the end of a long install just trying to get everything buttoned up. I was surprised how well it actually idled with 1 and 3 plug wires reversed but any throttle input would cause similar symptoms.
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Old Oct 29, 2009 | 07:35 AM
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I put all 4 on the Driver's side in reverse order one time on a stock car and it sounded like it was camming, ran great too..just had a slight miss..lol
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Old Oct 29, 2009 | 09:04 AM
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It only does it when idling. I don't think it would be a misfire though. I know all the wires on the plugs are right, unless the ones on the opti are wrong.

The builder told me that the motor was at TDC when I got it back. So I installed the opti like it should be and every 1/4 turn when I adjusted the valves was right so I'm positive that is fine. I guess I'll have to just check the wires going onto the opti.
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Old Oct 29, 2009 | 10:20 AM
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Got a converter in? A bolt may be loose, or out. Also, check the mounts to the engine, may be off, or loose causing the engine to move some or go out of balance at the higher rpms. Just my ideas where to also look.
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Old Oct 29, 2009 | 11:22 AM
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i was thinking motor mounts or a balancer/flexplate/flywheel issue. is the balancer neutral balanced?
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Old Oct 29, 2009 | 11:45 AM
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Originally Posted by sweetbmxrider
i was thinking motor mounts or a balancer/flexplate/flywheel issue. is the balancer neutral balanced?
the thing is, the motor sits 100% still in the engine bay, it doesnt shake the slightest like you would think it would if it were out of balance. I suggested the motor mounts beacuse the "vibration" gets worse as rpms go up. but they're not solid mounts.
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Old Oct 29, 2009 | 11:56 AM
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How big is the cam?
Did you change your motor mounts in this project?
Have you verified that plug wires 6/8 are not crossed?

Who tuned it?
Did you check for vacuum leaks?
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Old Oct 29, 2009 | 01:07 PM
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Originally Posted by James Montigny
How big is the cam?
Did you change your motor mounts in this project?
Have you verified that plug wires 6/8 are not crossed?

Who tuned it?
Did you check for vacuum leaks?
oh, its not my car, im just trying to post what I can to hopefully help him out more

Cam IIRC is 236/242
motor mounts are the same as before, used a BMR tubular k-member, so the passenger side mount base is different now.
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Old Oct 29, 2009 | 01:10 PM
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Originally Posted by reamo04
oh, its not my car, im just trying to post what I can to hopefully help him out more

Cam IIRC is 236/242
motor mounts are the same as before, used a BMR tubular k-member, so the passenger side mount base is different now.
Sorry, I was asking the OP
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Old Oct 29, 2009 | 02:08 PM
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Originally Posted by James Montigny
How big is the cam?
Did you change your motor mounts in this project?
Have you verified that plug wires 6/8 are not crossed?

Who tuned it?
Did you check for vacuum leaks?
Cam is a 236/242
Motor mounts are the same but base on driver side is different because of the BMR tubular k member.
I'll check the wires tonight but I know that the driver side is fine.

Car has not yet been tuned.
No, haven't checked for vacuum leaks.

One other thing that has been brought to my attention is that my coil wire was arching out on the water pump when I first tried to start it. I'm gonna replace that wire tonight if the plug wires are not crossed.
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