guess what this sound is?
Guess the sound?
- Thread starter Doubeleive
- Start date
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Tonyrodz
Resident Resident
Flywheel?
OP
OP
that was my first thought and after I banged around on the exhaust and cat and stuck a stick in against the frame to hold it tight I was like crap I hope not
it only does it when the AC compressor is on and you can only hear it on the passenger side, but when you pop the hood you cant hear it there either but I was still thinking it could maybe be the compressor or something, reached in with a stick and pressed on the pedal while listening to the passenger side and it made no difference idling up or down, kind of went away when idling up.
so then I thought maybe it was the fan blower motor (maybe) so I turned that all the way down, made no difference, turned the ac on/off, on/off, sound goes away and comes back with ac compressor??? so.....wth? lol, turns out it's the passenger side transmission heat shield, whew got lucky. those freaking heat shields make the weirdest sounds had one under the hood on my nbs make a horrible noise took about 3 weeks to find that one, it's 100deg outside right now I'll get under there in the morning and try and bend it a little tighter, dodged the bullet this time.
Tonyrodz
Resident Resident
Damn lucky for sure. I had a flywheel crack almost all the way through--where the bolts go through to the crank. It was holding by a hair. That was after I had my new trans installed. Guy kept saying it was a heat shield.
SnowDrifter
Full Access Member
Sounds like either cats are falling apart internally or a heatshield rattle
A ****** up flywheel sounds pretty deep
A ****** up flywheel sounds pretty deep
Tonyrodz
Resident Resident
My flywheel was making a tinny "ting" noise. Sounded alot like a heat shield ting.
SnowDrifter
Full Access Member
Interesting. Haven't heard one that yet that wasn't rod knock like. Good catch
SnowDrifter
Full Access Member
Got excited and didn't quite read the thread fully. Glad you got it solved!
OP
OP
I'm 99% sure it's the heat shield, reached under there momentarily and touched it and was loose, funny I thought I was hearing some noise over the past couple weeks but wasn't quite sure until I parked next to a wall and left it running and went over to the passenger side to unload a couple packages. I guess with the ac running and a warm idle it "rattles"
OP
OP
got under there today and sure enough one of the heat shield bolts was a couple turns loose, it tightened and then kind of felt like it got loose again a tiny bit like maybe it's stripped or could still use some cranking (hard to judge) so I just left it at that, the noise is gone so I guess if it comes loose again down the road I will just throw a couple washers on it to get around whatever thread might be stripped.
CountryBoy19
Full Access Member
Hmm... that makes me wonder... I have a "tinny" sound when I get on it... I assumed it was piston slap but I don't know that I've ever heard what piston slap actually sounds like. I wonder if it's just a heat-shield.
OP
OP
check around the back of the engine bay and down towards the exhaust manifolds, I had mine smacking against the exhaust before just bent it back a little and noise was gone, but the sound it made was terrible
When you get on it? Sure its not pinging? Just an idea...
CountryBoy19
Full Access Member
I guess it's possible... it's only at or near WOT
SnowDrifter
Full Access Member
If you don't have access to a scan tool to check, easy route is to toss premium in there next fill up and evaluate
CountryBoy19
Full Access Member
I have a Tech 2, where do I check for that?
Am I just looking at timing numbers or is there a specific place/procedure to watch for detonation?
Last edited:
CountryBoy19
Full Access Member
SnowDrifter
Full Access Member
There should be something in there to let you see live data. Look at misfires, timing advance, and knock retard. Also pull up your oxygen sensor voltage. If it's hanging near 0v, it's lean. If it's hanging near 1v, it's rich. Bouncing between the two is normal, if it's constantly at one extreme or the other, it might warrant further investigation.
OP
OP
so I was having the Yukon transmission and transfer case flushed today so I drove the Silverado around and kept hearing a rattling noise (again), thought maybe the heatshield had come loose again, got underneath there and banged on it nope...this time it was a broken heat shield on the driver side cat, only rattled under load. went by the muffler shop and they 
it back up for free. now I think it needs a a/c tensioner sounds like your killing a cat for the first 10-15 minutes in the morning 
it back up for free. now I think it needs a a/c tensioner sounds like your killing a cat for the first 10-15 minutes in the morning 
