Car vibrates/shakes under full boost at low RPM/WOT

[Ski Bum]

This just started happening recently after installing some lowering springs. What is happening is when at low rpm's, around 2500-3k up to about 5k, at WOT and only when full boost hits (12psi), the entire drivetrain/engine starts to vibrate/shake quite severely.

The springs lowered the car about 2" up front and 1.9" out back. The car is by no means slammed, I have a 2 finger gap up front and back with stock sized wheels/tires.

The vibration is more noticeable in 2nd gear and not as apparent in 3rd, 4th, and 5th possibly because of the faster speeds drowning out the vibration or the gear ratios?

I also just had the wheels balanced and aligned to with zero toe all around, -1* of camber both front and back. I used to have a pretty bad shimmy at freeway speeds before balancing the wheels but that is gone now.

I have heard that sometimes lowering high mileage cars (mine has 115k) can put stress on the axles enough to cause vibrations? What I cant figure out is why it only happens under full boost? I do have a boost leak on the exhaust side of my turbo but that was present long before lowering the car and the vibration only began after lowering it.

Any ideas?

 

[Seano04]

Take a look at your motor mounts and tranny mount. I experienced a similiar problem and it ended up being my tranny mount was loosing the rubber insert. I replaced them with the insert kit from SBR for like $80.

 

[Ski Bum]

Take a look at your motor mounts and tranny mount. I experienced a similiar problem and it ended up being my tranny mount was loosing the rubber insert. I replaced them with the insert kit from SBR for like $80.

I have replaced 3 of the 4 mounts I know of, the front, left and right mounts, one of which I think is considered the tranny mount. The only mount I have replaced is the small one under the intake manifold.

Are there any others?

 

[Ski Bum]

Is the vibration related to the car being lowered??

 

[DScooten]

I have an auto 97 gst that I just lowered and it does the exact same thing. Only started when I lowered it. I don't get it it because my car has urethane mounts and new axles and wheel bearings. I've heard it could be needing a camber kit but why would that make it shake?

 

[turbo98eclipse]

sounds like a tranny problem. it happens so much in 1st gear because it is the biggest gear and creates nore torque. as you go through gears the reduction becomes greater until you hit 5th (overdrive). the more torque (boost) you hit the more it will shake