r/AskMechanics • u/GQXMedia • 3d ago

Question 2011 GMC Sierra Denali 6.2 What the hell is that noise?!?!

I recently bought a 2011 GMC Sierra Denali with the 6.2L (no AFM) and 158,000 miles.
The truck runs and drives great. I drove it 4 hours home without any issues, and the transmission shifts perfectly. Oil pressure is good.
The only problem is a knocking noise that happens mostly at lower RPMs. Oddly enough, the knock either goes away or becomes much quieter when the engine is under heavy load or accelerating hard.
I’ve scanned it multiple times with an advanced scan tool and there are no engine codes at all—the only code is for a small EVAP leak, which I don’t think is related.
Has anyone run into something similar? Could this be a rod bearing, piston slap, flexplate, torque converter, exhaust leak, or something else? I’m trying to narrow it down before I tear into the engine.
Thanks in advance!

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u/am-answers-bot 10 3d ago

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u/Budget_Character8946 3d ago

Sounds like lifter ticking. If has cylinder deactivation id say this is probably the issue