False Knock Originating From Drivetrain?

By 94BigBlazer
April 10, 2008 in Ask A GM Technician

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94BigBlazer

Posted April 10, 2008

Hey guys, hopefully one of you may have an idea. I've been battling a knock retard issue with my 2002 Sierra Denali (LQ4, AWD transfer case (NVG149) and the 4L65E (HD) Transmission) for a while now.

Quick lowdown - I'm getting max 8º KR during WOT 4-2nd and 3-2nd downshift. I've eliminated every possible scenario with the engine, exhaust, suspension, tested the knock sensors, it's definitely not detonation. It's Westers 91/93 tuned, yet it will still behave the same with my stock PCM installed. I scan and log with EFILive.

So I'm down to something transfer case or transmission related.

If you have intricate knowledge of these components, and what could possibly causing a noise that would be interpreted as false knock, please speak up.

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