Strange vibration...

Hi Ryan ! Quick check for you ...Pull the dust cover and unbolt the 3 convertor bolts. slip the convertor back and start the motor..
I bet you won't have a vibration !
This is a fairly common issue with lockup convertors.
Good luck and let us know !
Happy new year Boss !
Dave Lewis

 

Sorry, I don't have any suggestions for you, but please don't shoot yourself.

Sadly, though, I think your hunch is what I would think too or maybe the harmonic balancer on the engine, but I don' think those really go bad.

 

I had a torque converter bolt loosen up on me a while back and that did the same thing you're describing.Good luck with it.

 

Does the ZZ383 use a neutral balancer? I've had hellacious vibrations with slipped damper rings on external balance motors. Good luck

 

I have disconnected the converter ... slide it all the back and had the vehicle raised a little in the front ... to try and figure out if the torque converter was bad.

IT WAS

 

These other guys MUST ... type faster than I do

 

Could be as simple as an out of phase u-joint.

 

texas dirt dobbers . back of the ballancer or in the pullys .i find this as more common than converters or ballancers . if your problem was instant and no issues the last time out then check for mudd .c

 

Yeah Shifty, we all know the boss hasn't been revving this thing enough to slip the balancer ring ! LOL !
Seriously , I doubt a new balancer on a gm crate motor would slip with normal street use. Can't say it's impossible, but it's doubtful.
Ryan, good luck getting it home .
Dave

 

Ryan says it happens in Neutral & Park, as well as when driving. U-joint won't be turning in Neutral or in Park......I hope!

 

Sound stupid but check your wires and plugs for fouled plugs

 

also possible cracked flexplate if it is they usually get worse fast ​

 

Had a fan do that once on a friends car. It was the small dowel (shaft?) waterpump with a big (corvette?) fan on it. In short the hole in the middle was larger than the shaft it had to index on. Would only wobble at a certain rpm but was a pretty bad vibration.

Converter thing is likely too.

 

Ryan, I'll put my .02 cents in...... harmonic resonance like what your talking about, could come from the converter. But if it was the converter, you would be having problems downshifting. You should rule out the exhaust. Check all the maifold bolts, pipe flanges, and all. Also check all of your brackets on the front of the motor. Make sure there isn't anything hitting and so on. Most time a vibration like this is due to something of this nature. Very simple. Of course we always think the worst, by over-thinking the problem. Hope you find it.

Mott

 

I missed that, somehow (too much cold medicine, perhaps). He's also added that it came on slowly, which is further proof its not an out of phases u-joint. This possibility can be safely ruled out.

 

Maybe you ran over a mattress. I got this email recently and it sounds just like what you described.


This guy ran over a mattress and decided to keep going. The ensuing jumble finally whipped around enough to put a tear in the gas tank, the subsequent lack of fuel is what finally brought this vehicle to its knees.

It had still managed to drive 30 more miles decently with a 60lb tangle wrapped around the driveshaft.

This genius complained that the vehicle had a "shimmy" when driving at high speeds.

This is what the dealership found.............

 

but the bolt does come loose.

and I have seen the lower pulley bolts come loose on the crates and cause the same issue.

 

Yes RACEFAB, I have seen them do that .
Ryan, have you checked the balancer and pulley bolts yet?
I would hope that when you installed the motor you torqued the balancer bolt and locktighted it when you installed the pulleys.
I think the boss has had some issues with this trans before, and is getting fairly well frustrated with it !
Let us know what you find.
Dave

 

Sounds like converter to me too. I have had a similar problem and am experiencing it again with my 38 chevy coupe. Used a ****** that was sitting for a long while and the clutch material and other solid matter gets thrown to the outer edge of the converter, when it sets for a while this material settles to one side and will cause an out of balance condition when its put back into service.

 

I'm glad someone started a thread for this. I have a nasty vibration in my '62 C10 that I've been trying to chase down. I'll check for all of these things. I'd also like to add that I had the same issue once on '59 GMC and it turned out that a balance weight had popped off my drive shaft, but that wouldn't explain yours doing it in park. Hmmmmm

Looks like I need to get under my truck and check my converter bolts and a little of everything else while I'm there.

 

There's 2 ways to balance a 383 (so I've been told) : Internally or Externally. Which do you have?
I've had LOTS of GM flexplates fail, usually accompanied with a ringing sound - not just a vibration.

I'm wondering if you have the wrong flexplate and/or balancer, and it just took this long to shake a good converter loose?

 

Cracked flex-plate?

 

so what was it?

 

Turn the radio down,it's just the Beach Boys.

 

Get some "posi traction rear end conditioner"( smells like ****!!lol) & put it in your ******.You'll be amazed at how good the car will run.alot of time that "vibration" is the converter in a between mode, not know whether to lock up or not & its basically a chatter , not a vibration. i hate a T bird that did the same thing
JimV

 

Good thread. I'm having issues like this right now, bought a 60 impala that was a 3-4 year project. Hasn't seen the open road yet. It was back firing when we pulled it onto the roll back. The story is, 327 gone thru, bored 30 over, new pistons, etc.....rebuilt 350 turbo. Well the first thing we found was wire #2 and wire #3 was hooked up wrong on the firing order. Ran alot better then but loaded up bad. Then we found that when the 4 barrel edelbrock was rebuit the choke linkage was put back wrong and the choke wouldn't open all the way. Fixed that. Ran alot better but I noticed a vibration on acceleration. Did it in park. I had a petronix flame thrower distributor from a parts rig I bought so I put that in with new flame thrower wires and plugs. Still did it. Noticed the harmonic balancer looked big for the year so I ordered the correct one and installed it. Each time it gets a little better but that vibration is still there and just bugs me. I put it up on the hoist today and watched the flywheel/torque convertor while it was running. A slight wobble, not much. Then I came home and found this post. Tomorrow I'm taking the altenator belt off and running it. Then I'm might try backing off the convertor and running it. Much useful info in here.