Allan

Since the car is just about ready for the road ... I figured I'd throw this one out there. I get a vibration when the engine is around 3500 to 4000 RPM, not bad, it's just there. I have never noticed it until I got the flywheel replaced. The old one was cracked. Now, immediately, I assume the bastards put an unbalanced flywheel in, but after a while, I'm thinking maybe not. This is when I noticed it - it could have been there .. I just didn't notice it until I got the flywheel replaced ... SO ...

The car is 12 years old, flywheel is brand new ... I can't see them putting in an unbalanced flywheel - so what would the possibility of the harmonic balancer just being bad? - I'm thinking of trying that first ....

Any other suggestions or opinions? That's pretty much the only real thing holding me back from taking her on the road again (besides dry-rotted tires )

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The Camaro Shrine
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'88 Camaro IROC-Z 350 TPI
'98 Grand Prix GTP 3.8L SC

"Yea, though I walk through the valley of rice,
I shall fear no Turbo; for Torque art with me."
- Cullan Hooley

Allan

Oh, and it happens with engine RPMs, not vehicle speed, so from the torque converter forward is the problem area ... it vibrates when in park on the driveway.

ede

hey allen long time no see. could it be a miss at 4000rpm? is the tune up good?

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ICON Motorsports
1st & 3rd

Allan

Hey, ede! Yeah, long time! I still have you on ICQ, next time I see you, I'll plop you a message .. eh?

Anyway ... yeah, I thought it could be tune up too. I practically rebuilt the entire intake on the 350 TPI, including having the fuel injectors cleaned and flowmatched by Rich at CruzinPerformance (he did an excellent job, by the way). Replace the plugs w/ AC Delcos, wires (NOT Accels), cap and rotor. Fuel filter, air filter ... pretty much the whole works and it STILL vibrates.

Like I said, though ... I only noticed it after the flywheel change ... perhaps I didn't realize it until the flywheel change ... who knows, but I did to the timing change replacement at close to 100K. I didn't bang the harmonic balancer off, but like other people have said, age and mileage may cause that rubber seal to just break up. I don't know. I'm hoping for a cheaper fix I guess. To have the flywheel checked will be a little bit more dough ...



------------------
The Camaro Shrine
------------------
'88 Camaro IROC-Z 350 TPI
'98 Grand Prix GTP 3.8L SC

"Yea, though I walk through the valley of rice,
I shall fear no Turbo; for Torque art with me."
- Cullan Hooley

TransamGTA350

iTrader: (2)

I had an 86 IROC with a 5-speed and a similar problem. The pilot bushing was worn out allowing the input shaft on the transmission to move and causing the clutch disc to be off center. This happened because the input bearing on the transmission went bad and caused the shaft to move and wear out the bushing. I didn't replace it when I did the tranny and the clutch, but I noticed it after it was put back together.

To check if this is the problem, while at rest and the engine running, leave the clutch disengaged and rev the engine and hold it above 4000rpm. If the vibration is there, then it's the flywheel or balancer. If it's not there, then with the transmission in neutral, and the engine above 4000, let the clutch out. Keep letting the clutch in and out to see if you can get it to vibrate. If you can, then it is most likely the bushing, or a bent input shaft. A bent shaft will be consistant all the time, but a bad buching will be a different amount of vibration every time you let the clutch out.

89 Transam GTA, a few bolt ons

Allan

Small problem ... mine's an automatic ..

ede

maybe look at the torque converter bolts and trans to engine bolts make sure they're all tight. i don't think you could see or get to the flex plate bolts, but that would be something else to look at. it doesn't seem likely that the damper went bad right after the flex plate swap.

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ICON Motorsports
1st & 3rd

Allan

This car has been known to do things like that ... hehe ... I'll take it back to the place that did the flywheel swap (and tranny rebuild) and see if they can tell what's up. I won't rule out the damper, though ... that can still cause it ...

TransamGTA350

iTrader: (2)

You said flywheel, so I assumed it was a manual. So you mean you had the flex plate replaced?

Allan

Yeah, that's what I meant. I've always called it flywheel ... don't know why but guess it's a hard habit to break ...

Pat Hall

iTrader: (31)

Just a simple check you might want to do. The flexplates on our cars actually have a weight on them. You might want to drop your inspection pan and see if there's actually a weight on your flexplate. I found this strange when I bought a new one for my car. I was wondering why an internally balanced engine would have a weight on the flexplate. I think the reason is because the one piece rear seal crank flange is perfectly round instead of oblong like the old two piece cranks. Whatever the case, if they installed a flexplate with no weight on it, that would definitely cause a vibration problem. If that checks out ok, I'd be looking at the harmonic balancer next. But since you said the problem more than likely coincides with when you replaced the flexplate, that would definitely be my starting point on diagnosing the problem.



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89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."