Hi Guys,
​​​​​I have a Lexus IS 350 RHD. When driving, a rattle / buzzing noise comes from the mid-rear passenger side. It only comes momentarily around the 1600-1800 rpm point and goes away right after. Most probably, some component is resonating at that specific engine frequency. This happens only in drive, not in Park or Neutral. Sounds like an exhaust rattle, but couldn’t see anything loose or hear any obvious noise after tapping the whole exhaust with a mallet.
One thing to note though, the rear driveshaft flexible coupling is starting to crack ever so slightly. No idea if that would cause this.
Much appreciate any insight on this.
Cheers

 

Hi, I'm sitting with the same problem.
My car: 2014 IS 350 RWD

Another car with the same issue: https://www.reddit.com/r/LexusIS/com...is_this_noise/

Mine happens only when the car is warmed up, on load(low throttle), all gears and around 1600rpm.
I cant get it to do it revving stationary as well.
Nothing has changed or got worse.

Ive done the gearbox and diff service. Everything looked healthy in the oils according to the shop and did not change the sound.

I suspect is something in the exhaust (muffler or cats) since it is in every gear with a certain resonance and a certain load depending on amplitude.
Other than that didn't see a mount that's worn or something loose.
All heat shields are tight and bolts are tight, no obvious exhaust leaks are apparent.
The springs on the axle-back part with the mufflers would be another guess.

Nothing rattled as well when I put it on a ramp and hit the exhaust (Could be that It had cooled down enough by then)
I think I have to drive it till its hot and immediately put it on a ramp and hit it then see.

I'd love to figure this out on my car as well.
If you've got any more hints or let me know.

All the best!Last edited by MalKaasBroodjie; Today at 01:16 AM.

 

I did an entire thread on this a while back for my 2023 IS350 RWD. Same noise as heard in the reddit video. Mine has done it since around 6k miles and I'm now up to 31k. Been getting slightly louder over time. Had the dealer look at it twice now. Last month they had the car for three weeks trying to figure it out and concluded: "You have a bent brace along the subframe that could be causing it." After they quoted me a crazy price to fix that, I declined. Been meaning to take it to my friend who owns a body shop and continue the investigating there.

What differs with mine is it's louder when cold or before the engine has had a chance to warm up (still does it when warm). Same rattle/buzzing sound right before it shifts and right after it shifts, usually at 1400-1500 rpm under light throttle. Will not do it in Park if I rev the engine. Only when driving with light throttle application.

Here's where it gets complicated. As I mentioned, the noise started at 6k miles. At around 21k miles, I ran over some debris on the freeway. That is likely what caused the bent brace the dealer found. But they are pointing to that as a possible cause and won't proceed further because of the damage. So it's on me now to get that bent piece fixed. Which I will do, but I have a feeling it will not solve the noise which started well before I hit the road debris. I just have a bad feeling I'll spend the money to fix a bent brace for nothing. But either way, the noise has to be found somehow so I will likely have it done.

 

Thanks for sharing your thoughts guys. Have been doing some digging about this issue online with no apparent solution.

Had a chat with the Google AI assistant, and this was its take:

Quote:

The "resonating/vibrating buzz" you are hearing is almost certainly caused by Item 075: Tail shaft rear rubber coupling starting to crack.

Why It Matches Your Symptoms
* The 1600-1800 RPM "Sweet Spot": Rubber couplings often have a resonant frequency. When the rubber is cracked, it loses its structural integrity and can oscillate or "buzz" at a specific engine frequency.
* Back Middle Underneath Location: This coupling is located directly in the center-rear of the car's underbody, precisely where you are hearing the noise.
* Only While Driving (Under Load): This part only rotates and transfers torque when the car is in gear. In Park or Neutral, there is no tension on the coupling, which explains why the noise disappears.
* "Sounds Like an Exhaust Rattle": A vibrating rubber coupling can transmit high-frequency harmonics through the chassis that mimic the sound of thin metal rattling

However, the cracking on the flex disc is quite miniscule and it doesn't have any weird play on it either. As MalKaasBroodjie said, the muffler springs might be a good place to check, and I will come back with an update once I get a chance to mess with those.
Cheers

 

I have a 2020 is350 that has the exact same noise you guys are describing. Mine happens around 1,400 rpm at light throttle. I have spent a little time banging on the exhaust and have been able to recreate a sound that is similar by doing that. It sounds like there is something rattling loose inside the exhaust when I bang on it. Around the mid pipe area if memory serves me correctly. I have not taken the exhaust apart to see if that is the case. The car has 57,xxx miles currently. It was bought with 34,xxx miles and has done it since the day it was brought home. It does not seem to be getting any louder.

I'll be curious to see if you guys find anything.

 

This thread is gold. I have lived with this noise for most of the life of the car. I am surprised not one dealer has been able to find the source or a fix. Please, if anyone finds the exact source and fix, post it here. I'd do anything to have a normal-sounding car.

 

Quick Update Guys

Put the car up in the lift and had a look today. The cross brace underneath the midpipe area had a slight bend, and I thought that was the culprit. Straightened it out and reinstalled, but the buzz is still there. @Fizzboy7, you were right mate. I doubt that yours would make any significant difference either.

However, roughly guessing by the general area that the noise usually comes from, the rear muffler shields might be a good place to look next. I saw that they are fitted to the body only from one side and have a little bit of room to move on the other side. The free side has a tiny rubber piece that would act as a bumpstop/ dampener if or when the shield comes into contact with the body under vibration. I think that particular shield might produce a buzz if it's slightly deformed or changed shape and comes into contact with the muffler or car underbody.

Will be looking into it and will keep you guys posted.

Cheers

 

Thank you so much for the update and going through all the physical trouble! I monitor this daily to see if anyone has found the spot or solution. It is the only thing holding me back from loving this car, so desperate to get it fixed! Please keep us updated on any new findings! Thank you.

 

Could it be coming from inside the muffler itself? Maybe one of the baffles is loose?

 

heat shields loose or bent could be the problem.

 

What seems odd to me is most people are saying the sound only comes at 1400 rpm while moving forward. That is the case with mine too. So if it had to do with something caused by outside damage, wouldn't the sound vary? Because everyone's damage is different. Yet it always seems to be the same spec for the sound. This is what leads me to believe it has nothing to do with damage or something being bent. It's got to be a built-in piece creating the racket.

 

Agreed that a loose/ broken muffler baffle could make a noise like that. However it’s quite hard to identify when the car is stationary since the noise only comes when the car is under load. I’ve been unable to replicate the noise by banging on both mufflers with a mallet.

None of the heat shields, exhaust pipes, mid pipes or exhaust hangers/ mounts around the rear of the car seems loose or rattly.

What’s left to check is basically the engine, gearbox and diff mounts and all of them are in pretty good shape.

 

I'll throw this out there in hopes to not complicate the search. I swear my noise sounds more like it's coming from the engine area, not from underneath or behind me.

 

Maybe check the cats for damage. And the springs on the midpipe flange.

 

Quick update. I had my car up on a lift at a body shop and the metal brace plate only had a tiny ding on it. This was the piece the dealer stopped at and said, "we can't go further due to this damaged piece." So there's no way the noise is coming from a tiny ding on the plate. It is not touching anything around it and it's completely secure. Also checked everything else underneath the car while it was up and there was nothing loose nor any other visible damage anywhere. The vibration noise has to be coming from something more internal or deeper up. So I'm back to square one. But at least I know it's not what they were saying it could have been from. Now I've got to convince the dealer of this or maybe try another one (I'm still under full warranty).

Any new updates from anyone?