Rattle from rear and dealer can't figure it out

[Lttlwing16]

Hey Folks,

Driving a 4cyl 15' Legacy with 80k miles. Within the last year I have developed a pretty loud rattling sound that is coming from muffler/rear driver side of the car. I have had the car at the dealer three times, and had the muffler replaced and one more forward heat shield around the catalytic converter removed, all to no avail. 

The sound is intermittent. It's nature sounds like something metallic vibrating at a medium frequency against the body (plastic or coated metal). It only occurs between speeds of 5-35mph, always around 1k-1200 RPM, and most commonly when the automatic transmission is in low 4th & 5th gear. While operating the car in manual mode, the issue is almost non-existent as the car will not allow the transmission to stay in a high gear too long before "downshifting" out of the gear. 

On the last visit the dealer ruled out the engine and transmission mounts as issues. 

It seems the vibration is caused by the CVT reverberating and coming through the exhaust or muffler heat shield. I have tried stuffing steel wool, aluminum foil balls around the heat shield around the muffler all with no difference. I have removed the spare tire, and all trunk contents, no difference. 

Since it is linked to the drivetrain, it could also be the rear diff, axle, or rear driver wheel bearing? CVT going out?

Thoughts?

Thanks,

David

[silverton]

are you positive it's on the exterior of the vehicle?  It's amazing the amount of rattle complaints I get and the car is just filled with all sorts of goodies that rattle in the cargo area. 'rec customer remove personal belongings'  for due diligence make sure the spare tire holder is tight.

[Lttlwing16]

39 minutes ago, silverton said:

are you positive it's on the exterior of the vehicle?

Yeah, I took the spare and all the other contents out of the trunk and it didn't change.  I Also checked the license plate as it's only screwed in to the top, but it also didn't help. 

What it honestly sounds like is the tailpipe rumbling against the bumper plastic. but there is plenty of clearance around that. 

Wondering it if it's the rear differential.. 

[silverton]

Has the car been in any kind of incident with the rear?  I know there are some thin metal shield type things around/inside the rear bumper.

[Lttlwing16]

2 minutes ago, silverton said:

Has the car been in any kind of incident with the rear?  I know there are some thin metal shield type things around/inside the rear bumper.

No, not while I've owned it. That said, it sits in a parking lot most days, so who knows if someone bumped it at work. I felt around on the rear bumper, but it feels like it's securely attached. 

Good thought though, I'll try to take a more in depth look this weekend. 

[MoleMan]

What about the rubber mounts the rear cans are held in place to?  I know I had a rattle and it was the fact the muffler came loose from the rubber mount.

I had a similar issue in my 3.0R. same type of sound.  Turns out it was the cat heat shield.  But for some reason the noise was coming from the rear.  Sounds sometimes can be nowhere near where we think they are coming from.

Another thought is the tin dust shield behind the wheels.  That can get bent real easy.  I have had issues with that I. The past having the same noise you are describing as well.

[iyalla]

I bet its the axle. Sounds like a resonance vibration only at certain revolutions per minute and under load.

[Lttlwing16]

23 hours ago, MoleMan said:

What about the rubber mounts the rear cans are held in place to?  I know I had a rattle and it was the fact the muffler came loose from the rubber mount.

I had a similar issue in my 3.0R. same type of sound.  Turns out it was the cat heat shield.  But for some reason the noise was coming from the rear.  Sounds sometimes can be nowhere near where we think they are coming from.

Another thought is the tin dust shield behind the wheels.  That can get bent real easy.  I have had issues with that I. The past having the same noise you are describing as well.

Checked the rubber mounts today, and they're good. 

Cat shield was just removed by the dealer because it had been damaged by a previous owner. 

I have plastic dust shields behind the wheel, and tried some tricks to isolate those and they weren't the issue. 

Thanks for the thoughts, and keep them coming! 

[Lttlwing16]

22 hours ago, iyalla said:

I bet its the axle. Sounds like a resonance vibration only at certain revolutions per minute and under load.

This is what's getting me, WHAT is the CAUSE! Even if it's the exhaust, it shouldn't be sustaining vibrations strong enough to shake the whole car. 

[MoleMan]

3 hours ago, Lttlwing16 said:

Checked the rubber mounts today, and they're good. 

Cat shield was just removed by the dealer because it had been damaged by a previous owner. 

I have plastic dust shields behind the wheel, and tried some tricks to isolate those and they weren't the issue. 

Thanks for the thoughts, and keep them coming! 

The dust shields behind the rotors should be real thin tin.  Did you replace them with plastic?  

Another thought is maybe some small rocks or small pebbles under a plastic cover somewhere.  I have had this issue on every Lexus and Toyota I have ever owned.  Sometimes it gets annoying.  It just rattled like a spray can sometimes.

 

 

[Lttlwing16]

14 hours ago, MoleMan said:

The dust shields behind the rotors should be real thin tin.  Did you replace them with plastic?  

Another thought is maybe some small rocks or small pebbles under a plastic cover somewhere.  I have had this issue on every Lexus and Toyota I have ever owned.  Sometimes it gets annoying.  It just rattled like a spray can sometimes.

 

 

Sorry, yeah I haven't checked the brake  dust shield yet. Could be it, it's coming from that area. 

 

I was able to briefly reproduce the sound by pressing my orbital sander to the muffler, but not with much reliability. 

From that, it sounds as if something in the muffler is rattling (despite it being brand new) and resonating in the cavity it sits in which is lined with a tin heat shield. 

[DougKelly20]

Dumb question....could it possibly be the decklid plastic? All our WRXs had problems with that....the plastic against the metal ... Put some foam padding in and it was gone...

[Lttlwing16]

13 hours ago, DougKelly20 said:

Dumb question....could it possibly be the decklid plastic? All our WRXs had problems with that....the plastic against the metal ... Put some foam padding in and it was gone...

Hey Doug, I've been meaning to write in and say I figured it out. After a day of trouble shooting, I isolated the rattle as coming from the muffler or heat shield above it. Since it was cheap and relatively easy, I went ahead and replaced the three rubber grommets that hang from the body and the muffler and exhaust supports couple to. PROBLEM SOLVED. 

While I can still feel the motor bogging down, the rattle it caused is gone. The old one's must have lost their plasticity and were transmitting the vibration into the body of the car. 

I've made an appointment to get the CVT looked at to see why it's wanting to stay in 5th gear and bog the motor down, which is causing low frequency vibrations at around 1000-1200 rpm.