I have a noise that I don't really know how to narrow down.

Engine-
2001 5.3 with 125K miles. Absolutly stock.

Problem-
While stopped, trans in D, I can raise and hold the RPM's to 900-1000 and hear a constant steady rattle/knock. It also does it if ideling thru a parkinglot and I give just a liiiittle bit of gas.

During a cold start it knocks like hell, but goes away for the most part after a few minutes. I'm thinking piston slap there. Pretty sure I'm confident in that.

BUT, the other noise? WTF is it? I tried capturing it on video, but too much background noise/distortion to hear anything pertaining to the noise.

I've heard the flexplate, or maybe it was the TC bolts, can work loose? Could they make this sort of noise?

ALL help is appreciated. Thanks.

 

I would hop under it and just double check the TC bolts, that way you can at least narrow down the possible causes.

 

Check the torque converter bolts for sure first. Mine tapped at idle and lite throttle and it was just one bolt loose

 

Can I get to the TC bolts thru the larger round silver plug/plate thing? Looks like it may be an access port??

 

Yep, thats exactly what its for.

 

I had the same problem it was the cats. Sounded like a rod knock. Crank it and beat on the cats with a hammer a little and see if it changes.

 

+1

if you hit the cat and here it rattle thats what it is, had this happen to me

 

AHH! I didn't even think of the cats. Had that on my old 93 Z28 i had, the sheild seams busted loose and rattled like hell.

Thanks, I'll be under the truck looking for this fix as soon as I get the drivers door hinges pins/bushings done.