Pushrod tap?

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afpj

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Hey alI , 2002 Yukon with 174k miles. I've read all sorts of threads about piston slap and lifter tap. I think I have closer to lifter tap sound but coming from lower part of engine rather than topside. It only happens after a little rev of the engine when cold, and only when the rpms come back down, not when rpms go up or at peak of the rev, and I'm only talking up to 2000 rpm max. Hope that made sense. The noise is gone after engine warm. Does that sound like pushrods to you gurus? Hopefully not a main bearing, but it's a tapping sound not a deep knock. Oil pump? Any opinions appreciated thank you.
 
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rockola1971

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Main bearing bad sounds like a growl.(before it spins) Similar to a ball bearing going bad. Your pushrods are fixed (essentially a spacer). The adjustable part comes into play with the lifters which are hydraulically adjustable. Your problem is most likely in your lifters and/or rocker arms (need adjusted). I would start at the rocker arms. Pop the valve covers off and do the valve adjustment procedure.
 
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afpj

afpj

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Thanks for feedback. I wasn't sure since the sound 'seemed' to have come from below, but localizing them is always a bear. I tried the screwdriver technique since I don't have a stethoscope, but trying that when revving engine is just too noisy. It figures I just changed valve cover gaskets and didn't think to break out the feeler gauge.:doh2:
 

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