I have an 94 GT and I did a burnout 2 months ago and the car hasn't been right since!! After the burnout I took off and the car started to shake. It shakes AS SOON AS the tranny goes into 2nd gear, which is around 22MPH, (I have an automatic) and continues to shake all the way up until around 50 - 60MPH while decreasing in intensity. It drives fine with no shaking in 1st gear or if I have the shifter in 1st gear. It also starts to shake when I put the car in any gear other than Park or Nuetral. And if I stand in the rear of the car I can hear the exhaust making an huffing noise, I took the car to a exhaust shop and they said the engine was running bad (of course) and it was sucking in air! The shaking feels almost like I'm rolling over peebles. While all this shaking is going on there is no "check engine" light. Another thing to add is a couple of days ago I started the car it seemed like everything was fixed!! I drove around for about an hour with no shaking whatsosever then all of a sudden it started to do it again while I was driving.

I've since replaced my tranny, torque converter, MAF sensor, throttle position sensor, idle air-bypass valve, and fuel filter. And it still does the same thing. Any help would be greatly appreciated!!

How badly does the engine run? does it idle like when you first got it? have you tried compression check on all cylinders? it could be somethings possibly relating to rings, balencer, crank, rod, basically bottom-end engine... but i dont understand the part of the 2nd gear, what that has to do with it. if it was in the tranny, id say planetary gears, or valve bodies, but you say youve replaced the tranny. How much HP are you pushing? you might have twisted your driveshaft or U-joints. Centrifigal parts have a weird way of acting up when they want to. One way to see if you can make it is jack up the rear end and try and get it up to that speed and have someone see if they can hear or see the noise... it might even be in the axles. OK, enuff ranting by me tonight, im gonna get another beer.
Let me know
~*Adam C*~

Check to see if your harmonic balancer is in good shape.
Check to see that your engine and tranny mounts are not ripped.
And check your U-Joint . They should have absolutely ZERO play.
Good Luck

there are some simple things you should check.

By what you explained, it could be a huge list of potential problems.

First, you need to find out if it is the engine, the drivetrain, or the suspension. If it ran fine for 1 hour and then went back to it's usual shake, I would suspect the engine. Things that are mechanical like the drivetrain or suspension, usually fail and stay failed.

start your car, open your hood, and have a friend put it into drive (someone you trust won't run you over, lol). Is the engine really shaking? I mean really shaking? A little shake at idle in neutral is normal. Also, while you are at it, have them move the gear selector from reverse to drive a couple of times. Watch the engine and see how much it moves. With a load the engine will torque on the motor mounts. If it is a broken mount, the engine will move a lot.

I am guessing it is the motor. Possibly a vacum line leak. Check all your vacumm lines to make sure they are hooked up. It could also be a loose spark plug, fouled plug, a loose plug wire, or a failing plug wire. These are very common things!! How long has it been since you put new plugs, wires, and replaced your vacuum lines?

I just changed my spark plugs, wires, cap and rotor today. I noticed that 1 of my plugs was soaked in oil. Changing the plugs stop the shaking but how did oil get all on the tip of the spark plug? There isnt any smoke coming from my exhaust either.

If you're getting oil on your plugs chances are from wear are valve seals or something from up in the heads. Rings could be bad, but you'd notice the compression loss. oil up isnt un-heard of, but less common.
~*Adam C.*~

I read your post earlier today and did not have time to comment until now. Of course it is very hard to diagnose a particular situation via electronic communiction. All of the suggestions were what I would of said as well. I'm happy to hear that you corrected your situation. As for the spark plug that was soaked in oil, you problaby have a pistion oil ring problem or a really worn out valve guide causing the oil to soak into the cylinder at a rate that it cannot be burned off quickly, so it sticks to the plug. If you have a leak down tester or have one performed by a reputable individual, it will tell you the condition of your engine.
It sounds like you have a worn out engine and its rebuild time. How many miles/kilo's are on the engine by the way? If it's relitivley low maybe just a hone and new rings will cure the oil burning if your cylinders are still round.
Frank...