I recently developed a very bad vibration issue in the motor. I know its not in suspension or drivetrain because it happens in park.
Symptoms are: Start it and it shakes. Start revving it and you get to about 1500 RPM and thats the worst spot. The whole car is shaking and theres an ungodly loud vibration noise. It also adds a ping sometimes. Then as you rev up higher itdies then comes back then leaves. about 1700 its fine then 2000 it comes back again. Then 2200-2800 fine. Higher then that its a rythmatic vibration.
Me and my brother have it diagnosed as possibly the Harmonic balancer. But honestly I have no idea.Any ideas as to what else it could be? Any help is appreciated. Thanks in advance.


82 Trans Am Chevy 305 Just switched to Holley Carb.

 

I forgot to mention that I also had this issue where Ive had a bolt or 2 or 3 (I know of 1 for sure) falling off. I found a bolt in the driveway and I know it came from my car but I hav eno idea where from. I dont have a cover on the bell housing over the Tourqe converter.

 

Better crawl underneath and check if you're missing any flexplate or torque converter bolts.

 

I got down there this morning and checked out the flywheel to tourqe converter and nothing is missing. and I didnt see any other missing bolts. I checked the motor mounts. Everything looks good. This sucks.

 

Did ya check the flexplate-to-crankshaft bolts?
There's 6 of them I think. They are close to the flexplate center.
You'll probably have to unbolt the flexplate-to-torque converter bolts, slide converter back a little and look up in there.
You won't be able to get a wrench on them, but you should be able to see them.

 

The noise could still be from the transmission in park, because stuff is still whizzing around in there when the engine is running.

Also if the transmission is not tight to the supports, it will move around just from normal engine vibration.

If you found bolts, maybe they could be from the rear axle anti tramp or stabilizer bar where it attaches with rubber clamps to the transmission.

It sounds worth checking if the transmission supports are coming adrift

 

Check your harmonic balancer crank bolt. Also check to make sure the 3 bolts that hold your crank pulley on are still there. Sounds stupid but my crank bolt shook itself loose and I ended up going down the road and hearing the harmonic balancer rip off stripping the key way off the crank. Watched as a flaming harmonic balancer shot out the rear of my car after seeing my floorboards shoot up from where I ran it over. It ended up costing me 7 months downtime, and a new 350 swap.

 

What and where is the flex plate. Ive never heard of that before. Is it also called somethng else??

 

Flexplate is very similiar to a flywheel. Its in the same spot.
Flexplate is for auto trannys. The torque converter bolts to it with 3 bolts.
A flywheel is for manual trannys. It's a lot heavier and has a big smooth surface for the clutch to push aginst.
Both have teeth on the outside edge for the starter to engage with.

 

Checked it today. Transmission is solid. Crank Pulley is solid. Didnt have time to unbolt the tourq converter to check the crank/flexplate bolts.
Im gonna try and have a buddys cousin (who is a mechanich) listen to eat and see if he has any ideas. Im stumped and its pissing me off.

 

Just thought, it could be the motor mount rubber failed or the bolts snapped and you have part of them fallen out. I've had that on other cars.

 

Nah Ive triple checked the motor mounts. Theyre solid as a rock. Is this problem possibly a harmonic balancer. or am I way off.

 

I said YES!! Check it. Make sure that the outer balancer is inline with the inner part. The rubber wears out after a while and causes the outer part to walk. Also check any other pulleys and make sure they are spinning true. If any are off you will definitely feel it.

 

Would I be able to see the harmonic balancer shaking around visibly under the hood.

 

are you sure it is not a missfire happening? it can hit all 8 cyl but, miss alittle on one or two and do just what you are saying. is the bolt fine thread?

 

Not sure actually. Ive been meaning to check the timing and make sure its still good. and I should change all the plugs see if its firing well. Ill do that tommorow morning.

 

my latest postulation is that it might be the distributor. Its centrifical advance and Im thinking it might be going bad and causes misfires as I move through the RPMs. Is this a possibility or would it be all or nothing with the distributor.

 

Torque converter? The last strange vibration I had to troubleshoot(not my car) ended up being a bad torque converter. Removed the bolts on the flexpate/converter, slide the converter back a bit, started it up and the vibration was gone. Just a thought...

 

Good Idea. Maybe Ill try that tommorow if its not rainy outside. Thanks a lot.