Vibration Diagnosing Help - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 7 (permalink) Old Aug 3rd, 18, 12:11 PM Thread Starter
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Mike
 
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Vibration Diagnosing Help

I need a little help diagnosing my vibration. Seems between 2000 and 2200 are the worse in any gear. If you push the clutch in, and coast/idle, it's smooth. If I bring the rpms up to that rpm range with clutch still pushed in, the engine vibrates a little, but is really exaggerated when clutch is engaged and carries through the driveline and putting a load on it.
The 454 is externally balanced, stock rotating assembly, with stock damper, converted from auto to manual. The pulleys are a OE serp setup off a newer sbc and can't see any wobbling. And the flywheel and clutch are new, and those are balanced at the factory, right? When i installed the gear venders, i had a new shaft made and balanced. one thing I didn't do was install a 1/4" spacer under the tranny mount that came with the GV. Would raising the GV .25" make a difference? and only at certain rpms? There aren't different harmonic balancers for auto and manual?
I just don't know how I should go about diagnosing further

67 Chevelle 454, M21
Gen IV 454 (out of C30 ), 390 heads 1.88/2.19 valves by Vortecpro, with ISKY Hyd Roller cam (at 050 218 int./228 exh, lift 530 int./552 exh.), RPM performer intake, Fitech 600HP, Dougs headers, and M21, Gear Vendors OD, 3.73's, UMI Suspension, Viking coilovers.
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post #2 of 7 (permalink) Old Aug 3rd, 18, 1:50 PM
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Ole
 
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Re: Vibration Diagnosing Help

The cause of a vibration can be just about anything that rotates. Your particular vibration seems to be noticeable at a certain RPM range, rather than at a certain speed, so that would indicate that you could all but eliminate tires/wheels, rear axle, driveshaft and probably transmission as the cause. This leaves anything between the balancer and the clutch assembly. From the way you describe this vibration I would lean towards flywheel and/or clutch. As for factory balancing of clutches and flywheels, I wouldn't bet the farm that one or both are not your problem. If you've ever sent an engine and related components off for balancing, did your pressure plate and/or flywheel come back with holes drilled in them? Chances are they did. Mine always do. So you may want to send your flywheel and pressure plate out for balancing.

As for harmonic balancers, they are gender neutral, automatic and manual use the same balancer.

You may want to try that spacer, although I'm betting 1/4" won't make a difference.

Also, I've never owned an externally balanced big block, so I don't know the eccentricities of those engines.

Just my .02. Good luck and keeps us posted.
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post #3 of 7 (permalink) Old Aug 6th, 18, 12:44 PM
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Re: Vibration Diagnosing Help

Any gear (same engine RPM), and smooth while coasting is usually engine related. It can be the water pump, fan, pulleys, clutch, or bad engine balance. Pull all the accessories one at a time to check those, clutch is a more work but can be done. If you still have vibration under no load, it's the balance job. This assumes you don't have any misfires or tuning problems. Those can make a slight balance issue much worse, esp. excessive advance/pinging.
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post #4 of 7 (permalink) Old Aug 7th, 18, 10:37 AM
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Re: Vibration Diagnosing Help

Sounds like a flywheel imbalance to me.Make sure you have an externally balanced flywheel.396,427 and 400 are different.400 is externally balanced too but have a different part number. Of course small block is different to.

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post #5 of 7 (permalink) Old Aug 8th, 18, 9:17 AM Thread Starter
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Mike
 
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Re: Vibration Diagnosing Help

Well, not exactly what I wanted to hear, but it makes sense. I didn't have the clutch and flywheel balanced before assembling.

67 Chevelle 454, M21
Gen IV 454 (out of C30 ), 390 heads 1.88/2.19 valves by Vortecpro, with ISKY Hyd Roller cam (at 050 218 int./228 exh, lift 530 int./552 exh.), RPM performer intake, Fitech 600HP, Dougs headers, and M21, Gear Vendors OD, 3.73's, UMI Suspension, Viking coilovers.
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post #6 of 7 (permalink) Old Aug 8th, 18, 11:24 AM
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Chris
 
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Re: Vibration Diagnosing Help

what flywheel did you buy? Some FW's like the McLeods require a weight that bolts on to work with an externally balanced engine.

Have you checked your driveline angles? Download the tremec app for free, and check your angle at the transmission, then driveshaft, and then rear end. This will find your operating angles.

1971 Chevelle SS454, T56 Magnum 6 speed, 3.31 Posi

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post #7 of 7 (permalink) Old Aug 8th, 18, 12:10 PM Thread Starter
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Mike
 
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Re: Vibration Diagnosing Help

Quote:
Originally Posted by -SS454- View Post
what flywheel did you buy? Some FW's like the McLeods require a weight that bolts on to work with an externally balanced engine.

Have you checked your driveline angles? Download the tremec app for free, and check your angle at the transmission, then driveshaft, and then rear end. This will find your operating angles.
oh man, it's been like 5 years. I don't remember installing any weight though. can I see this weight looking through the dust cover on the bellhousing?
I haven't done anything with driveline angles either. Still running the stock trailing arms which don't have adjustment. I'll try that app, thanks!

67 Chevelle 454, M21
Gen IV 454 (out of C30 ), 390 heads 1.88/2.19 valves by Vortecpro, with ISKY Hyd Roller cam (at 050 218 int./228 exh, lift 530 int./552 exh.), RPM performer intake, Fitech 600HP, Dougs headers, and M21, Gear Vendors OD, 3.73's, UMI Suspension, Viking coilovers.
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