Im posting this here because I need to get some results for this problem.

My car has been shaking violently after my LT1/M6 swap.

Ive changed just about everything in terms of suspension and powertrain, and I dont know what could be causing it to shake so bad.

Ill explain when it is happening:

I first noticed it when I would get to 80 mph, and let it cruise. While it is crusing, and i pop it into neutral it starts to shake, and what im feeling it body roll from driver rear to passenger front, and passanger rear to driver front. at that point, when i pop it into 4th the car stabilizes.

next, i started noticing it big time when I went up and down a steep bridge. IT would start while I was going down the bridge and let off the gas...and again, pressing the gas stabilizes it more.

please...i need a solution to this.

Some background info.
KYB's in the rear, Stock DeCarbons in the front.

eibach lowering springs

C6 wheels (18s front/ 19s rear)

stock panhard (kept on from v6 through swap: my understanding is that is was universal)

stock lca's kept on from v6 through swap: my understanding is that is was universal)

1 piece driveshaft (lt1)

new sway bars new mounts

new tranny mount.

anything else please let me know.

I would like to get this problem resolved, so anythign is helpful.

 

Is the engine idleing ok? If you're sitting still in neutral at idle do you get any vibration?

if not, does the vibration change when you let out the clutch as you're moving in neutral?

 

theres no swing from left to right up until i hit a certain speed....

it continues to happen today

 

clutch in or out?

I've never seen this before but because it happens when you're in neutral it sounds like something in your drivetrain is out of balance... although I'm not sure why it doesn't happen under power.

Did you get an oe rubber tranny mount or a stiff aftermarket unit. I've heard stories of folks breaking that mounting point when they put the aftermarket unit on... that may cause all sorts of weird issues.

 

I've figured out how to better explain the vibration.

It feels sorta like turning the wheel from left to right quickly at high speeds...the car is going straight, but it is moving up and down on its sides...do you guys follow???

 

well first of all I hope youre not daily driving the car ... sounds like a dangerous situation. You may want to have someone observe the car from another vehicle to see if there's anything noticeable in the drivetrain, like the rear axle wandering or somthing like that. If the rearend is set up wrong I could see something like this happening... under power everything is being torqued into a certain configuration, but in neutral it might oscillate.

Anyway... be careful... you may want to just take it to a garage and have an expert look at it.

 

unfortunately it is my daily driver.

as i said, it just came out of a fresh sway, and I changed everything on the powertrain.

This just started happening recently. The car was runnin hard and pulling strong as hell out the hole at first, but then outta nowhere...

I dont knwo the problem..honestly....its driving me insane. I think i drive it better when im drunk!

 

When changing the engine to a V8, did you use the front struts and springs for a V8? My brother didn't and had the same problem.

 

For the sound of your description, I get the feeling the rear-end is dancing under the car, possibly due to driveshaft misalignment which may be caused by LCA bushing or panhard bar bushing collapse. While not very technical, you can check the distance from the top of the each rear tire to the inner wheel well. I suppose you could also check the length of each LCA from bolt to bolt as well.let us know what you find.
Doug

 

i checked the bushings, and they all seemed okay to me. its always a possibility though...

im sure it has to do with my powertrain...it has to be the cause...

 

okay...Update...

Ive triggered whats really going on. Ive learned that the swinging from side to side occurs from the shifting of 3 to 4...does that help any?

 

Ever figure out what was happening? Sorry to dig this up from too long ago.

 

well...i still havent really figured it out...but i will tell you that once i put my stocks back on the car did stabalize a bit more, but it still does it...and its quite dangerous...thank god for my daily driver...

 

Hmm.....A scary situation indeed.

1) Check that all bolts holding the sway bars are tight. If the sway bars are from the V6 camaro then I think you'll need the ones from a V8 camaro to handle you new motor combo.
2) Check that all bolts holding the LCA's are tight.
3) Check that all bolts holding your Panhard Rod (Bar) are tight. The panhard bar centers the rear end, if its lose, then your car will "wonder" all over the road.
4) Check your pinion/driveshaft angles. You want a difference of two degrees between the them - anything more will result in excessive vibration.
5) Did you get the correct Transmission Cross Member for a LT1 Camaro.

In regards to the LCA's and the Panhard Bars that you had on your car - were these basically stamped pcs with the bushings pressed into them?

 

from the first post you said it was happening when you put it in neutral or down a steep bridge

my first instinct says check the rear end
sounds like a problem in the ring and pinion while coasting
you said you changed the whole powertrain, does that include the rear end? if so, where did you get the rear end