Is this chattering noise my transmission?

[Delta1Seven]

My truck makes a chattering/rattling noise that only occurs after a cold start. It noise consistently starts about 6 minutes after startup, and once the truck is fully warmed up, the noise goes away. This happens every single cold start, at almost the exact same time each time.

I’ve already taken it to the dealer, but they said they couldn’t hear anything. I’m just curious if anyone has experienced something similar or has ideas on what could cause this.

I've pushed on all my exhaust hangers and most metals under the truck and it doesn't go away. It seems like it's coming from the transmission. My truck is not in the transmission TSB.

2024 about 8K miles.

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[icetaco]

Heya, we're twins. I posted the same thing back in November -
Post: https://www.tacoma4g.com/forum/threads/rattle-grind-on-cold-start.16725/
2024, Off Road, Non-hybrid, ~4900 miles. Not on transmission TSB. No codes, vehicle drives completely normal.

I haven't taken it to my dealer yet, but I'm about to once I hit 5k miles. I have the cat shield underneath, which is where it sounds like it's coming from - and that thing has a big ol proprietary screw that I'll need help from the dealer to get off.

FWIW, same exact thing as far as the delay. Never on an absolute cold start. I took a picture of the engine temp because this was a more reliable way to know when I'd start hearing it (more or less when it sits at that first ~1/5 mark, is when the noise is the loudest).

Did the dealer dismiss your video? That seems pretty definitive -

I did some searching in other places, and someone had posted this picture of his heat shield that he said was near the cat - and that those two heat shields were smacking each other rather than being loose. (the photo below is not my photo, that's the photo he posted). Unfortunately that's also under my cat shield so I can't poke at it myself, but given that the truck has to hit temp to start making it, I'd want to avoid poking around hot metal!

 

[Delta1Seven]

Heya, we're twins. I posted the same thing back in November -
Post: https://www.tacoma4g.com/forum/threads/rattle-grind-on-cold-start.16725/
2024, Off Road, Non-hybrid, ~4900 miles. Not on transmission TSB. No codes, vehicle drives completely normal.

I haven't taken it to my dealer yet, but I'm about to once I hit 5k miles. I have the cat shield underneath, which is where it sounds like it's coming from - and that thing has a big ol proprietary screw that I'll need help from the dealer to get off.

FWIW, same exact thing as far as the delay. Never on an absolute cold start. I took a picture of the engine temp because this was a more reliable way to know when I'd start hearing it (more or less when it sits at that first ~1/5 mark, is when the noise is the loudest).

Did the dealer dismiss your video? That seems pretty definitive -

I did some searching in other places, and someone had posted this picture of his heat shield that he said was near the cat - and that those two heat shields were smacking each other rather than being loose. (the photo below is not my photo, that's the photo he posted). Unfortunately that's also under my cat shield so I can't poke at it myself, but given that the truck has to hit temp to start making it, I'd want to avoid poking around hot metal!

Thanks for the reply. I’m non-hybrid as well.

The noise is extremely consistent, which is why I’d be surprised if it’s the heat shields. For them to rattle only during that narrow warm-up window, they’d have to be sitting at almost the exact clearance where thermal expansion causes contact only when partially warmed, but not fully cold and not fully hot. Since we’re talking about metal expanding only a few hundredths of an inch, it seems a bit unlikely. But I hope I am wrong!

That said, it’s still possible, and honestly I’m hoping it is something like a heat shield rather than anything internal or mechanical.

I don't have a lift but I'll try to crawl under my truck to take a look. Do you know if the photo of the heatshield you provided is from underneath the truck or looking down at the engine bay?

 

[icetaco]

From your video -

Different angle - but the you can see the stamped arrow right near the exhaust hook. The lip of the other shield is facing the camera directly. But given the video angle, can also see they aren't really touching.

I see my dealer on Tuesday. Plan is to get there an hour or so early, so the truck can cool, and walk out with the tech so we can all listen together 🥲

 

[Yotota]

Aside from getting Toyota to fix it, the only option I can think of is to use a metal rod to poke around while the noise is occurring. Not sure I'd trust wood around the cat/downpipe.

And if you touch it to your trans case and hold it to your ear, it will act like a stethoscope to amplify any internal noise. Or just use a mechanic stethoscope if you have one.

It could be one of the welded exhaust heat shields that popped loose, and only rattles at a certain point of thermal expansion like you said. I had an exhaust leak on an old truck that did the same thing from a small crack.

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