Spacers between torque converter and flex plate??

[Guest bastaad525]

Hey, posting for my friend again. The one with the '64 Nova with the 350 motor in it.

 

He very recently has developed a strong vibration, directly related to engine RPM. The motor was recently fully rebuilt. There's no odd sound or anything to indicate anything like messed up bearings or rod knocking, and the exhaust note sounds fine, it doesn't sound like it's not firing on all cylinders. I checked for spark on all eight at the plugs so we know his wires and plugs are good. But the vibration feels similiar to if one or more cylinders weren't firing. Compression on all cylinders is good. No smoking or oil on plugs or anything indicating something went wrong with the rebuild.

 

He had some problems when he put everything back together, his friend was helping, and installed the torque converter for him. When he did, he didn't bolt it down tight enough, and a few days later my friend noticed a horrible knocking noise which was the torque converter slapping around. So he fixed that, and only about a month later now he's getting this vibration. So... not sure if that would have anything to do with that.

 

But the shop that rebuilt his transmission, the guy there advised him that he should use spacers between the torque converter and the flex plate, which he opted not to do since there were none before.

 

Has anyone ever heard of or done this themselves? Would this have anything to do with this vibration? He's wondering if it's even worth bothering installing those spacers now, which I'm thinking it won't make a difference, whatever is out of balance is already out of balance and will probably have to be replaced.

 

What other things could cause such a vibration? In the engine, I mean? Keep in mind, it's not making any odd noises... but I'm thinking it could be a bad bearing, slightly warped crank, warped flexplate... what else? I told him he should still consider his ignition as well even though it sounds and appears to be firing fine, he's got the old points type distributor and has had problems with the points. He also does get a moderate misfire at higher RPM (revved to like 2000 rpm and holding it) and under acceleration, though no apparent misfire at idle, which makes me think something is definately going on with the distributor/ignition.

[jt1]

The spacers won't affect the balance any. It's pretty hard for an engine to get out of balance. About the only way that can happen is if the engine has an externally balanced damper or flex plate, and the ring on the damper turns, or a weight comes of the flexplate.

 

Sounds to me like he has wiped a cam lobe. Pull the valve covers, spin the motor over and see if all the rockers are moving the same amount.

 

John

[Guest bastaad525]

but a wiped cam lobe would kill one cylinder wouldn't it? Because his exhaust doesn't have that typical sound you get when one or more cylinders are dead. You wouldn't know anything were wrong with it at idle unless you sat in it and felt the vibration. Whereas I've had a dead cylinder on my Z before (fuel injector wire came loose) and as soon as I started it I HEARD the difference.

[Mike kZ]

If the cam is alright, no loose rocker arms, it could be that the loose torque converter cracked the flywheel. There could be hairline cracks you can't see. Unfortunetly you'll have to take it off to inspect.

[jt1]

If the cam's lost a lobe, usually it will change the exhaust note a little. I missed the part in your post about still running smoothly. Like Mike said, possible flexplate problems- maybe the front bushing in the trans is damaged from the convertor bouncing around, another possibility. Also check the fan and water pump. One time I lost about 2" off the tip of a fan blade, and it made the motor vibrate like crazy.

 

John

[80LS1T]

If the cam is alright, no loose rocker arms, it could be that the loose torque converter cracked the flywheel. There could be hairline cracks you can't see. Unfortunetly you'll have to take it off to inspect.

 

Thats what I was going to say. If you can get the inspection plate off you might be able to see if its cracked. Sometimes if the cracks are big/long enough you will see them coming down from the center of the flywheel. This will cause an engine vibration that feels like a misfire. Sometimes you will also hear a clicking noise from the bellhousing area, which is caused by the crack in the flywheel.

 

Also make sure to use loctight on the torque converter bolts(I use the blue stuff).

 

 

Guy

[dr_hunt]

The easiest thing to do is to remove the torque converter bolts and push the converter back as far as it will go, then start the engine and see if the vibration is still there. This will isolate the vibration as engine related or trans related. What trans is it?

 

I had a th400 that had the same problem and was disassembled several times before finally yanking the trans in favor of another one, which fixed the issue. I had been through replacement of harmonic balancer, fan, water pump, pulleys, flexplate, converter and the trans apart 3 times for inspection. All the while the trans builder claimed the trans was perfect! It was not and the replacement fixed that. The vibration was so bad that you couldn't see out the rear view mirror at any rpm over 2500 cause it was shaking so much.

[Guest bastaad525]

thanks for the tips guys.

 

yeah I'm starting to suspect the guy who rebuilt his trans as well... he's been having lots of odd problems, the guy rebuilt the trans once and it failed within months. The guy blamed it on my friend and said it was because he didn't use spacers between the flexplate and torque converter. Even with that though he rebuilt it again for free, and now not even a month goes by and he's got this vibration.

 

One thing that keeps me from thinking it IS the trans though is that the shake is there even in neutral at idle, and definately corresponds directly to engine RPM... if it were the trans would it happen out of gear? I would expect it to happen at a given road speed and never in neutral.

 

My friend did mention today though that he noticed a slight (very slight he says, I haven't seen it yet but I bet it's worse than he makes it sound) wobble to the harmonic balancer up front. Now this really sucks because the crank he bought brand spanking new, and I'm hoping for his sake he hasn't had this worn balancer chewing up the snout of the crank.

 

So that's my bet... harmonic balancer, or like you guys said, a screwed up flex plate, or both. The flexplate makes even MORE sense now considering he just told me he actually drove it for quite some time with that thing loose and rattling, and this guy... well, driving this car for him means doing a burnout every chance he gets, and that's not an exaggeration! So lots of high revving with a loose torque converter... very little doubt he did some serious damage.

[dr_hunt]

Been there, done that, still could be the trans, just cause it's in neutral doesn' mean the internals aren't turning. I had same symptoms, motor balanced and all, ended up the trans. Could be the harmonic, but like I said if you check it like I suggest, you'll know right away and won't be wasting time.

[Guest flite72]

I had the same problem in my truck after we replaced the torque converter with an aftermarket one. Since the converter is balanced all by itself, and the engine is balanced on it's own, once they mate things may not be in balance. Factory style converters and flywheels are designed and balanced together and then marked. This is why most tranny shops prefer to rebuild the stock converter and put it back in it's original position. I was getting vibration in neutral at 1500rpm and hard vibration during acceleration at 3500 rpm. I unhooked the converter from the flywheel rotated it one bolt put it back together. I did this 3 times before it fixed my problem. You may only have to move it 1 notch. If however you had absolutely no vibration but now you DO have vibration I would suspect a cracked flywheel or loose conterter to flywheel bolts or maybe even a defective stator inside the converter.