I have literally no idea why this sound is occurring. Possible piston slap?

Its nothing of concern really. it doesnt hurt anything. its just super annoying. I made videos just like yours. I put y pipe on when i did my headers and no longer had it, but couldnt stand the sound of the exhaust, so i put the stock y back in until i can redo the exhaust as a whole.

 

those stock cats are worth $$ theres platinum in them.. if you replace it, the shop should give you a deposit or core charge I believe. Anyone have experience with what these are valued at in scrap yards?
A buddy had his cat stolen in his 1st gen.. ended up straight piping in when he found out the replacement $$

 

I think I saw them close to 1k if I’m not mistaken? Could be more.

someone come steal mine. . I’ll straight pipe it.

 

OP, I bought my Tacoma sounding exactly like yours in the video a little less than a year and a half ago. I posted a thread on here asking basically the same thing and never really got a straight answer as to what it is.

Anyways, it has been almost a year and a half and I’ve put a little over 20k on the truck and the noise has not gotten any worse or more concerning. If you ever find an answer let me know lol, otherwise just keep driving it

 

I’m glad I’m not alone out here! I have strong suspicion that it indeed is our cats. Two here already removed theirs and the issue was resolved. However.. I’m just going to drive this thing until it can’t drive anymore

 

lol same plan I have, drive it until it blows up then buy a newer one and LS swap this one

 

my 2015 did it when I bought it with 50k on it. Still does it now at 85k. My buddies 3rd gen Tacoma does it and another buddies newer 4 runner does it to. Some are louder then others but it does sounds like a kNocking right near the CAT. I even had a 2021 tacoma SR5 as a loaner a few months ago when my truck was in for the CRC coating. It did it too.

 

Someone made an identical thread last week too.
What's up with the V6 noise. | Tacoma World

 

I have the exact same issue. 2015 Prerunner, 4.0 5 speed AT. Just bought the truck several weeks ago, 150,000 mi. Did not hear the noise at the dealer, or it probably would have scared me off. Truck was warm when I got there( violated one of my cardinal rules). I was going to buy a new truck but....
Can only hear it from the drivers side behind the wheel, under the truck. Cannot hear it from the engine compartment.
At first I thought it was coming from the transmission, but when I put my stethoscope on the trans housing it was whisper quiet, likewise on the oil pan, lower block. Then, I wrapped a tee shirt around my hand and grabbed the heat shield on the cat and the noise almost stopped. I put my steth on the cat and could hear it, put it on the upper exhaust manifold and could hear it. So, I removed the heat shield to see if that was the offender. What a nightmare. The little bolts all rounded off, which left me to have to hacksaw (blade only) the rear bolt which had welded itself to the strap and dremmel off one of the front. The noise was less with the shield off, but still there. I think the shield acts as an amplifier.
I also thought it was a rod knock, but like I say, it is whisper quiet at the oil pan with the steth.
I see your post is from May, did you come to any conclusions? At this point, I hope it is the cat, but 600+ is a big chunk on a hope/

 

Its a noise most of them make. Nothing is wrong with your truck. The new 3.5 even makes the noise. My Tacoma has had the noise since I bought it with 50k on it. I am now at 90k. Every 4.0 I have heard has this noise to some extent.