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Old 09-12-2017, 09:22 PM   #22
towbar
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Join Date: Jul 2012
Location: Marshall, NC....heart of the Appalachians.....aka, Gods country!!
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Re: Any idea on what this knocking is 72 C20 350

Quote:
Originally Posted by Stocker View Post
Have you tried to pin it down with a mechanic's stethoscope? Works better than a hose imho.

It doesn't sound to me like a cracked flexplate but I guess that's a possibility.... or loose flexplate bolts. As other have said, it sounds more like valvetrain to me.
Sounds deeper and not as high pitched as rockers or pushrods to me. I'm in the line of thinking of the loose or broken flex plate. Also look for the flexplate hitting the torque converter cover (inspection cover). Quick 4 bolt check to rule these out. Good luck
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