[For3]

e90post I am hoping those of you with more auto knowledge than me can help point me in the right direction. I (and a coworker) are completely baffled by a sound my car has starting making this week.

Timeline:

• Last Friday I got the BMW PE exhaust installed at a local muffler shop that I have had experience with. All was good Friday pre and post pick up.
  
• Weekend - drove with windows down all weekend to enjoy new exhaust. Noticed a fluttering sound on Sunday on deceleration or throttle lift while cruising in gear. Sounds went (and goes) away when back on the thottle and accelerating. Sound is noticeable when near a wall or another car.
  
• Monday - noticed same thing on drive into work but a touch louder. Took car back to shop thinking it could be an exhaust leak that manifested as clamps and new exhaust heat cycled and settled.
  
• Monday afternoon - shop calls and says they found a very small leak and it's all good. Pick it up and within 100 yards notice sound is the same as before. I am imagine they didn't drive it and it is partly my fault as I didn't go in depth with the explanation of what I was experiencing only that I thought there might be a leak.
  
• Tue, Wed, Thur - driving everywhere windows down to try to diagnose the sound. It is most noticeable under deceleration or throttle lift. It is cyclical, not constant so the higher the speed the more constant it appears, but the slower you go the further between "pulses". Almost sounds like a playing card in hitting spokes of a bicycle wheel. The sound is mechanical. If I blip throttle while parked in order to rule out the exhaust the sound doesn't appear. So I think it rules out the exhaust. I was able to get the sound to start to appear by going down a parking ramp with the car completely off. The sounds wasn't as loud but was starting to get louder and faster tempo before I had to apply the brakes. We also noticed sound doesn't seem as pronounced out of gear, so if cruising and hearing sound, then shifting into nuetral (I have a 6MT by the way) the sound was much quieter. It seems to be eminating from the rear and seems to be both sides but it is very hard to tell. Sound seems to dissapate by 1k RPM or coming to a complete stop and most times these are tied together. It's hard for me to differentiate whether this is exhaust, brake, or driveline related.

Possible culprits I have thought of:

• Exhaust leak at clamp(s)
  
• Brake pads due for change. However, light hasn't come on dash, computer says 8k to go. Visual inspection of outer pads doesn't scream pads, but last time I got oil changed they did say I would be due soon.
  
• Differential?
  
• Guibo or flex disc? - doesn't sound like the videos I have seen which seem to have clunking and vibration especially on acceleration.
  
• Wheel bearings - doesn't sound like it compared to the youtube videos I have heard.
  
• Heat Shield hitting driveshaft some how?
  
• Rock in brake dust shield
  
• Some foreign object under car?
  

Thank you in advance for any help or suggestions. I will try to capture a video and post it.

[Noir]

FWIW, I had a similar noise after my new clutch/flywheel were installed. Turned out to be the heat shield tapping the drive shaft... Definitely post a videowhen you get the chance!

[rjahl]

Originally Posted by Noir

FWIW, I had a similar noise after my new clutch/flywheel were installed. Turned out to be the heat shield tapping the drive shaft... Definitely post a videowhen you get the chance!

I would certainly check the heat shields. I had something similar happen to me.

[For3]

Originally Posted by Noir

FWIW, I had a similar noise after my new clutch/flywheel were installed. Turned out to be the heat shield tapping the drive shaft... Definitely post a videowhen you get the chance!

Originally Posted by rjahl

I would certainly check the heat shields. I had something similar happen to me.

Thank You!!!

That was the issue.

[boosthead]

Interestingly, I noticed the same sound this evening on my commute home. I know what I'll be doing tomorrow....

Is there an area that's commonly the culprit?

[Noir]

Originally Posted by boosthead

Interestingly, I noticed the same sound this evening on my commute home. I know what I'll be doing tomorrow....

Is there an area that's commonly the culprit?

When it was a problem for me, it was the area above the transmission

[Noir]

Originally Posted by For3

Thank You!!!

That was the issue.

Whew, cool beans!

[For3]

I've attached a picture I took last night which showed the issue. This was taken from behind the rear differential on the passenger side with a view down the driveshaft. You can see the heat shield touching it. I am sure this happened as a result of them taking out / installing the exhaust. I took a yardstick and reached and and bent the heat shield down as best I could to get a little clearance from the driveshaft. Next the time the car is up I will do a more professional job but I was able to this just sliding under the car.

[atmosphericM]

Glad you got it sorted. I had a feeling it was heatshield related.. I'm happy it was nothing major!.. because as I started reading your thread here.. I started fearing it was your differential heh. *whew*

[For3]

You and me both!