Squeaking / chirping underneath truck - SOLVED

YYC-SIERRA · March 28

Have you ever heard that metal squeaking / chirping sound from under your truck, kind of sounds like a chipmunk?

It's most likely your adaptive exhaust valve. The valve is spring loaded closed, and opens during the transition from V4/V8 from exhaust pressure.

Eventually they wear out and get rusty and start squeaking like crazy. They're easy to disable (lock fully open) with a screw or clamp, clothes hangar etc. Whatever you prefer.

I used a clothes hangar today and the difference was instantly noticeable. ZERO metal noise, no squeaking, the exhaust actually sounded calmer at idle.

Best of all, my idle smoothed out tremendously (AFM delete with stage 2 cam upgrade). I was experiencing sporadic rough idle during city driving. I just thought it was due to my cam upgrade since big cams aren't designed for smooth idling. Turns out, when we did the AFM delete, we should have disabled the adaptive valve!! It's SO much better now.

Edited March 28 by YYC-SIERRA

YYC-SIERRA · March 28

Just rotate the valve all the way CCW and secure it from moving. That's it.

If you ever want to reverse the mod, just take off the screw or clamp.

This is a MUST DO in my opinion if you deleted AFM and run in V8 full-time.

m3n00b · March 28

Did this right when I got my truck home with 10 miles on it back in 2016.

YYC-SIERRA · March 28

I can't believe it took me this long to figure this out. I didn't even know that valve was there till last week.

The chirping noise has been eating at me for over a year. I thought it was my camshaft from a lifter failure.

David W S · April 1

Well, this is timely! I decided to skim through the forums today. I've been having this problem since I bought the truck 2 months ago. I knew it had to be exhaust related as it came from the back of the truck (even when not in motion). It did not occur to me they'd put a spring loaded valve in the exhaust line. That just seems silly.