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11-17-2012, 11:09 PM | #1 |
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loud knocking noise coming from under motor
my 1987 gmc high sierra just started making a loud knocking noise sounds to be where engine mates to tranny i unbolted torque converter and noise goes away any idea what that may be
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11-17-2012, 11:16 PM | #2 |
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Re: loud knocking noise coming from under motor
were the TQ converter bolts tight?
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2008 Silverado Z71 RCSB 1991 GMC Jimmy 4x4 1976 GMC Sierra C15 SWB |
11-17-2012, 11:19 PM | #3 |
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Re: loud knocking noise coming from under motor
yes they were tight
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11-17-2012, 11:29 PM | #4 |
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Re: loud knocking noise coming from under motor
Likely a cracked flexplate. They're cheap and available at any parts store.
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11-17-2012, 11:31 PM | #5 |
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Re: loud knocking noise coming from under motor
I bought an 87 that had a bad knock. It was cheap and I was thinking it needed a new engine. I looked close and the flex plate was cracked at the mounting bolt area where it connects to the crankshaft. Look at that closely. You can see it with a good flashlight.
Frank Posted via Mobile Device
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11-17-2012, 11:32 PM | #6 |
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Re: loud knocking noise coming from under motor
i will have to check that out as this flexplate is maybe 8 months old thanks for the info ill look to see if its cracked
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11-17-2012, 11:51 PM | #7 |
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Re: loud knocking noise coming from under motor
A lot of newer flex plates seem to be cracking...
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11-17-2012, 11:58 PM | #8 |
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Re: loud knocking noise coming from under motor
I vote flexplate also. I thought I had a rod knock one also and the flexplate was acually broken but it still drove. I drove it 60 miles like that to the shop.
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11-18-2012, 09:23 AM | #9 |
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Re: loud knocking noise coming from under motor
Aside from swapping it out, isnt there a problem since the flexplate is balanced with the other rotating mass?...I know mine was when I built my engine
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2008 Silverado Z71 RCSB 1991 GMC Jimmy 4x4 1976 GMC Sierra C15 SWB |
11-18-2012, 11:12 AM | #10 |
At the body shop.
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Re: loud knocking noise coming from under motor
Usually the flex plate/flywheel is left alone. For that reason.
And 350's are nuetral balance 400's have a weight. Posted via Mobile Device
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11-18-2012, 01:06 PM | #11 |
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Re: loud knocking noise coming from under motor
I think the single piece rear main seal engines have a weight on the flex plate too.
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11-18-2012, 02:27 PM | #12 | |
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Re: loud knocking noise coming from under motor
Quote:
Frank Posted via Mobile Device
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11-18-2012, 02:54 PM | #13 | |
At the body shop.
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Re: loud knocking noise coming from under motor
Quote:
Posted via Mobile Device
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11-18-2012, 03:46 PM | #14 | |
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Re: loud knocking noise coming from under motor
Quote:
my machine shop required flexplate to balance on my one-piece rear seal block 5.7L 350 (USA racing engines....wop shop in Houston) let me be clear lol....I'm asking you guys for him and my own future reference if this would cause a problem with just bolting on another right out of box?
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2008 Silverado Z71 RCSB 1991 GMC Jimmy 4x4 1976 GMC Sierra C15 SWB Last edited by 88Jimmy4x4; 11-18-2012 at 04:02 PM. |
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11-19-2012, 12:32 AM | #15 | |
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Re: loud knocking noise coming from under motor
Quote:
I bolted one up to the targetmaster 350 in my 76 along with a yard fresh 700R4 & NP208 and rear driveshaft. Then I drove it from Arizona to Cincinnati with whipped ball joints... because I had more balls than brains. It ran just fine the whole trip. Pulled that combo in favor of the diesel that it's running now.
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1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...
And please let us know if and how your repairs were successful. |
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