I've been trying to track down this bad vibration for a year now with no sucess. It all started after I rebuilt my engine. Before the rebuild there were no problems, but now when I get up to about 45 and the torque converter locks up, I can feel a really bad vibration. It's to the point it shakes the car. It also is worse when decelerating and lessens when accelerating. I've tried putting the car in nuetral, and it seems to lessen the vibration, but it's still there if you're going 75-80.

I've replaced the rear end, the driveshaft, had the transmission rebuilt and have tried both my aftermarket and my stock torque converter. Nothing has had any effect on this vibration. I've been told because it comes on when the torque converter locks up that it is an issue with the engine's balance. However, it seems that if I'm doing 75 and pop it in neutral, then if it were an engine problem it wouldn't vibrate anymore, but it does. That makes me think it's somewhere from the output shaft back.

What does everyone else think? feel free to ask questions, I'm horrible at describing things.

 

did you torque the driveshaft bolts to the correct spec, or did you crank them down? that was one of my vibration problems...
i also would think that if the flywheel bolts are not torqed right, there would be vibration... doesn't hurt to check...

i would think that if it was your engine you would have false knock or a light come on... not too sure though...

 

Sounds to me like your engine isn't balanced. Try slowly revving yor engine with the car parked. If the car vibrates more and more as the rpm increases I think you have found your problem.

 

anyone else? bump for the morning crowd

 

did you check out the things mentioned?

also did you replace the transmission mount with a poly mount?
do you have an adjustable torque arm?
did you check your u-joints?

i think we gave you a pretty good start for checking your problems...
no one is going to know the answer off the top of thier head...

good luck, hope you figure it out... when you do could you let us know what the problem was...

 

U joints are brand new along with a LS1 driveshaft that was balanced before I bought it. Flywheel bolts were torqued correctly. I replaced the tranny mount with a polyurethane mount. engine mounts are still stock. stock torque arm with polyurethane mount. I see where you're going with this, but let me stress the severity of this vibration. I've felt other cars with slight vibrations from things like unbalanced wheels or driveshafts. The vibration I'm experiencing is pretty bad, it's at the point it causes the interior pieces to rattle badly.

 

I'm by no means an expert, but it could also be an unblanced or out-of-round tire.

Also it could go hand in hand with a bum tire check struts and front suspension.

You never said how the crank was balanced after rebuild. External, internal, or both.

As mentioned above engine balance, any vibrations from an unbalnced crank would be transferred thru the motor mounts to the frame of the car, regardless of being in gear or not. I know you mentioned that it does it at 70, but you didnt give us a definate response as to wether it was RPM specific or if you feel it when you rev without moving.

 

does it do it when your parked or just when driving? i'd say check tie rods, struts, body mounts if you dropped the front subframe to do the motor... if its just when driving. Or maybe even if the rear end somehow got bent a little. hope you get it figured out.

 

the crank was balanced to the stock internal/external. I hadn't thought about checking the front end suspension....I'll look into that tonight.

I've always thought it was a speed dependant vibration, just because it comes on at 45 and gets worse with speed, but I was told that it could be an engine vibration and once the converter locks up it transfers the vibration from the engine to the rest of the drivetrain and the car. I did however put it in park and slowly revved it up. to me if feels like it's got a slight vibration, but it's also got a big cam that makes it difficult to tell between the natural lope from the cam and anything that could be a vibration.

 

i noticed that you said it vibrates in nuetral doing 75.
perhaps it is a wheel bearing... or out of balance tires or even rotors...

 

agreed it sounds like wheel bearings.

 

list of things to check:

wheel balance
wheel or tire out of round
tire tread plies slipping.
bad shocks and springs
tie rods
alignment
ALL ball joints and bushings in suspension system
wheels torques properly (warps rotors slightly and causes vibes...dont care if you believe it or not it's true)

 

i believe you i had this problem with my zx2... the shop used ampact gun to put my wheels on and shortly after i noticed a vibration, so i took the car to another mechanic and he said to torgue all the lugs to 80-90 lb/ft...
and what do you know? he was right...