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Old 11-02-2001, 06:30 PM   #1
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Join Date: Oct 2000
Location: Henderson, NV., USA
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Car: 87 IROC
Engine: 5.0
Transmission: 700r4

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Flex Plate, symptoms?


Anyone no what signs would be associated
with a flex plate going out.
I have been experiencing a knock coming
from the extreme rear of the engine and
seems to be coming from the flex plate area
I have found 2 of the bolts that attach it
to the converter loose, I tightened them
but this seemed to make it worse. Is this
noise a sign of a cracked or out of balance
flex plate, and if out of balance what can
cause this to just happen out of the blue?
car is an 87 iroc 5.0 w/700r4 with 80,000
miles
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Old 11-02-2001, 07:06 PM   #2
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You probably got a crack around the hub of the flexplate. The loose bolts are probably your cause.
It will get worse, and if the crack completes a full circle around the hub, the transmission will no longer engage.

You might take a look-see around the area of where the crank bolts to the flexplate. (Look very close, could be a hairline crack) Normally the crack will create a complete circle all the way around - sort of creating a donut out of your flexplate.

P.S. You can brake those super heavy duty flexplates with a single loose bolt. I have !!! I guess there is so much force pulling on that plate, if one bolt comes lose it will bend the plate beyond it's tolerances ?

Oh yea --- It sounds like a rod bearing, or like rocks in a dryer!


Ron


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[This message has been edited by ronterry (edited November 02, 2001).]
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Old 11-02-2001, 08:49 PM   #3
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Thanks Ron it does sound sort of like
a rod knocking, which needless to say
got me very nervous, I will try and
look for any cracks, it is diffucult
since there is not to much room to look
I did find two loose bolts, so that
could cause stress on the plate and bend
it? I hope thats all it is and not my
engine, Thanks again Ron,
Jerry
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Old 11-03-2001, 08:39 AM   #4
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the few badly cracked flex plates i ever saw/heard sounded like a unreal loud growl. the minor cracked ones made no noise at all.

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Old 11-03-2001, 08:49 AM   #5
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I general agree with the rest, but also look at the starter ring gear welds. a broken weld will make the same noise. Inspect the Harmonic Damper on the front of the crank
while you are there. If it is going bad It won't nessessarily make niose, but will cause the flexplate to self destruct from vibrations.

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Old 11-03-2001, 06:35 PM   #6
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Thanks guys for your responses, just one
more question, does anyone know the part #
and diameter and number of teeth on a
flex plate for a 87 iroc 5.0 TPI w/ 700r4.
guy at parts store had a few listed, so I
thought I should ask people that know
which one would be correct so I don't
buy the wrong one. Thanks
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Old 11-04-2001, 12:22 AM   #7
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Well Napaonline is calling for a 153 tooth, but off hand I'm not sure. You might need to remove the old one first. I always used the 168 tooth, but that was on later 350.

You can remove the flexplate without completey removing the transmission, but it will need to come back/down a half a foot. Get a long 11/16 wrench for the crank bolts, and a case of beer, and your set. THREAD LOCK RED - don't forget.

Good Luck,

Been there, done that !!!

Ron



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Old 11-07-2001, 10:14 PM   #8
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Well guys it turns out that this knocking
noise is not the flex plate, I had it
looked at and it seems to be coming from the
converter or the pump, its a knocking sound
that you can hear at startup and a little at
idle, it gets louder when I take off but it
goes away when it shifts into OD. other than
that the trans runs and shifts just fine and
no noticeable slippage. It just seems to
make this noise when I put a load on it like
accelerate from a stop or get on it but
shifting seems normal. What can go in a
converter to maybe cause this or does a bad
pump mean I need a rebuild. Any ideas?
Thanks, Jerry
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Old 10-11-2008, 05:07 PM   #9
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Re: Flex Plate, symptoms?

I also have the same problem my87roc i have a 2000 camaro ss ls1 my transmission is doing the same thing although it tends to be less noisy when the car warms up after a bit i was told it could be the same thing torque converter of flexplate shifts fine runs fine just really worried about it. Any information would be greatly appreciated would like to fix the problem before it gets even worse lol thank you Pat
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Old 10-11-2008, 05:07 PM
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