Need some help diagnosing a Problem noise. - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-24-2006, 01:30 AM   #1
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Default Need some help diagnosing a Problem noise.

Someone who is located close to me but far enough away I cannot visit personnaly has a problem with their 95 SSEi.

Here is a brief description of the problem:

Quote:
It'* a 1995 SSEi. You can create the noise by just standing on the gas,
even part throttle. It'* a grinding that you can both hear through the
firewall, seemingly more on the passenger side, and slightly feel through
the chassis. The noise is most prevalent when there is more load on the
engine, as in when you accelerate from a standstill, or mat it from a roll
on. As the load decreases, the noise fades to nothing. If you're starting
up an incline, it'* much louder as the load on the engine is higher.

When the shift to second comes, the noise reappears as the engine is again
under load, and again fades off. By this we can tell that the noise is
generated at the input to the transaxle, not downline, because the noise
correlates to the engine speed, not vehicle speed.

My guess is it has to involve something with the torque converter because it
seems most prevalent when the converter is multiplying torque. I
corresponded with one mechanic who suggested a cracked flex plate.

Any help you can give is greatly appreciated. Also, how big a job is it to
change the flex plate if that is in fact the problem? I've done tranny and
converter swaps as well as a front cover replacement on my '87 Grand
National, but I think it'* easier to work on the rwd rather than fwd.
Should I be thinking about tackling this? Maybe you could give the 1000 ft
overview.

Kevin
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Old 08-24-2006, 01:41 AM   #2
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I should add that one mechanic I paid to diagnose indicated motor mounts - the main mount was of course broken, so I replaced it with a heavy duty mount as well as replacing the other with no improvement. They also indicated tensioner pulleys, but I find no evidence there is anything wrong with those (stethoscoped, nice and quiet), and the symptoms do not match that diagnostic. If there'* anyone in Vancouver who would be available to listen/help me with the problem, I'd be willing to stop by and compensate for time.

Kevin
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Old 08-24-2006, 02:43 AM   #3
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You said the sound on the passenger side is a bit louder, the torque converter is on the driver side. What kind of noise is it? Clicking? Knocking? Pinging? So you hear it at low engine RPM, at the higher the load, I'm thinking its your dampener... low RPM + load = bigger fire, slower rotation = louder, and so it be more noticable. if you're supercharged, it could be improper timing of the supercharger lobes if you had it serviced recently.

Some guesses from my understanding of the problem.
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Old 08-24-2006, 02:54 AM   #4
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The description could for sure point to something in the trans worn out..

where are you located at?

is there still good power?
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Old 08-24-2006, 04:28 AM   #5
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To characterize the noise, it can only be described as a growl or grinding. The transmission shifts solid.

I have to reject the supercharger lobes because I would expect that to be rpm based purely, not load based - pressure could arguably account for it but in playing with it I don't get a sense that it'* related. I also discount it being in the trans itself, because the noise starts before there is any motion of the car, including if I stand on the brake. This would indicate to me that it is before or in the torque converter.

I'm in south Vancouver but will happily travel wherever in Van/Richmond/Burnaby/PoCo area to get some advice.

Kevin
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Old 08-24-2006, 07:35 AM   #6
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You mention the trans seems to function properly w/o any indications of a problem correct?

Have you watched the Harmonic Balancer while pulling on the belts to see if there is any flex or movement? It is a possibility. Affected by rpm and load.

Remove the belts and move each pulley by hand to feel if there are any binding or causing issues. Pulley'* would be also affected by rpm and load.

Like you.. I would put the trans and driveline onto a shelf as suspect for the time being based on your observations. This seems engine related.

Supercharger is almost definately ruled out as well.
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Old 08-24-2006, 11:51 AM   #7
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I wouldn't necessarily rule out the supercharger, as my '92 SSE */c makes a little grinding/growling noise that only occurs under light throttle in any gear but doesn't occur under moderate or heavy load or when there'* no load on the engine, and I believe the supercharger is making the noise...but I'd be surprised if a supercharger problem could transmit that much vibrational energy through the firewall unless there was another problem also. You said that you can feel it through the chassis, which may suggest the motor or tranny mounts. Also check all pulleys; there could be a pulley bearing problem that only occurs under load.
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Old 08-24-2006, 12:49 PM   #8
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The SC is easy to rule out by 'hand' with no belt.

Don't rule out the Catalytic Converter. My 95 did EXACTLY the same thing. Only under load, and based only on RPM'*. The core was rattling inside the cat. I found it by shaking the cat up and down. Side to side it made NO noise.

The lower frequency motion at lower rpm'* regardless of vehicle speed were shaking the exhaust up and down naturally, and the core rattled in a 'grinding' effect. Please note that it can be felt through the chassis and that the cat is slightly offset to the passenger side.

I too, thought it was the TC (on the input side of the trans). It was not.
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Old 11-22-2007, 12:37 AM   #9
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Default Noise

Did you find the fix for this problem? My 96 LSS has the same symptoms to the T. I am leaning toward the HB, but dont want to throw parts, ya know? Another suggestion was the cat converter, but it sounds much more like a rotatong assembly problem to me. Thanks,
JJ
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