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

Save my car, LS1Tech!

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Old Mar 31, 2013 | 08:46 PM
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Default Save my car, LS1Tech!

I have been chasing this god damn vibration for years. I have literally replaced everything from the flywheel and back. NOTHING IS FIXING IT.

You can feel it at about 70mph. It feels like the driveshaft is going to fly out of the car. If you have the car in gear, and you are accelerating, you BARELY feel it... But if you push the clutch in, thats when you feel it. Same thing in neutral. It is horrible, and I am afraid to drive my car. I can feel the transmission move, like its physically shifting. The mount is tight, I'm thinking maybe its moving? IDK...

I have done this to try to diagnose it:
Swapped out T56 transmissions
Aluminum Driveshaft from an LS1 car
Balanced the stock steel Driveshaft with 2 new U joins
Swapped out my rear end
Tried a poly transmission mount.
New Torque Arm (adjusted pinion angle to spec)
Panhard bar
Straightened and balanced my wheels
Tried another set of wheels
New flywheel/clutch/etc.
Relocated the Torque Arm

So... if anyone has some insight, or lives in my area and wants to take a ride... let me know. Please, I am about to drive this car off of a cliff and just buy an LS1. This is such a god damn headache

Last edited by ThoR294; Mar 31, 2013 at 09:38 PM.
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Old Mar 31, 2013 | 09:04 PM
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I don't see anywhere where you've changed or checked the transmission mount. I'd check there - it's easily accessible.
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Old Mar 31, 2013 | 09:14 PM
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Didn't you already have a thread about this?

What did you set your pinion angle at?
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Old Mar 31, 2013 | 09:37 PM
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I had a thread a long time ago... I also posted in another thread.

I put in a polyurethane mount as well, but it didn't fix it at all. Maybe I put it in wrong? (idk how that is possible). I have the rubber OE one in now...

I set the pinion angle to whatever GM recommends (I forget what that was). I set it a long time ago when I first got the Torque Arm.
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Old Mar 31, 2013 | 09:38 PM
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I chased this same problem for years on my Z28. Crazy vibration on deceleration. Only minimal vibration on acceleration. I tried everything to troubleshoot it. I went as far as swapping out the engine. Nothing helped until I got a new PST driveshaft. I do not recall the exact length, but it ended up being an inch or so longer than what I had. I tried a couple stock shafts too. Nothing helped until I got the longer shaft. I hope this bit of information helps you out. Also, as was stated, change out that trans mount if you haven't already. At the very least you can call a driveshaft shop and give them the measurements you have for your particular car and see what they think the driveshaft length should be.
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Old Mar 31, 2013 | 09:40 PM
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Factory cars come at 0* mild upgraded is recommended like -1* and wild is recommended -2*.
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Old Mar 31, 2013 | 09:43 PM
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That was my next step Chino Man. I just haven't had a chance to put my car on the alignment rack to send a measurement to PST to get it. I have always wanted one of their Driveshafts.

F0x: I think I did -1*.
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Old Mar 31, 2013 | 09:46 PM
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Running stock bell housing?
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Old Mar 31, 2013 | 09:47 PM
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Yessir
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Old Mar 31, 2013 | 09:50 PM
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Ever had the engine line honed?
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Old Mar 31, 2013 | 10:01 PM
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engine line honed? :O
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Old Mar 31, 2013 | 10:02 PM
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Yes. The mains line bored.
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Old Mar 31, 2013 | 10:08 PM
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engine is practically stock
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Old Mar 31, 2013 | 10:11 PM
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Did it start after the clutch install?

Are you using a bushing or bearing for the pilot bushing.
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Old Mar 31, 2013 | 10:13 PM
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was before the clutch swap. bearing.
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Old Mar 31, 2013 | 10:16 PM
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Bearings ew. If they fail they will destroy your input shaft.

Hmm. Running out of ideas here.
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Old Mar 31, 2013 | 10:19 PM
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Yeah. I have no idea. Apparently my uncle knows a guy who has been working at GM for his whole life and likes challenges... so maybe he can diagnose it. I may opt for a PST driveshaft just to see what happens. Good upgrade anyway
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Old Mar 31, 2013 | 10:20 PM
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I just put in a Strange 3" chromoly one.
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Old Apr 1, 2013 | 07:48 AM
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My thinking is since you feel it when you push the clutch in and especially since you can feel it in nuetral..has to be something to do with the clutch assembly. When you say you can feel it in nuetral...is that with the car sitting still or does the car have to be moving to feel it?

In an auto, I put the wrong flexplate in one time and that created a nasty vibration, could be felt with the car sitting still.
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Old Apr 1, 2013 | 08:03 AM
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only over 70mph, which leads me to believe its output shaft of the trans and back... nothing on the motor side. Its the same vibration with the clutch in or the car in neutral
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