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      01-18-2017, 01:50 PM   #27
BitchinManWheels
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Drives: Dinan M4, Z4, X5, Raptor
Join Date: Apr 2012
Location: Shavertown, PA

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Quote:
Originally Posted by Leng8093 View Post
Greetings all,

Long time (unregistered) lurker, first time poster in need of some serious help diagnosing a problem with my M4. I have searched high and low on this forum (and beyond) for anyone else who has experienced this issue (I've been to the dealership twice for the issue to no avail [they could not reproduce]) and I've found nothing. Needless to say I'm baffled and hoping I can leverage the vast knowledge and experience of the BMW and F80 community to help diagnose what's gone wrong.

The Problem
A noise (which sounds like a squeaking old mattress -see Exhibit-A for a recording) that was first noticed while I was changing gears in traffic and has progressed since then.

The Car
  • 2015 AY M4 6MT
  • ~8,600 miles (noise started at ~8,400 miles)
  • Dinan Stage 3 ECU - (installed after noise, prior was Stage 2)
  • Dinan Heat Exchanger - (installed after noise)
  • Dinan CAI
  • Dinan Exhaust
  • Dinan Suspension

*All mods (with the exception of the heat exchanger) were present on the vehicle thousands of miles prior to the first instance of the sound.

When does it occur?
  • Toggling steering wheel M 1 (All Sport+ besides steering) to M 2 setting ("non-sport" settings). Vehicle is stationary, in neutral, with foot brake engaged after 30 minutes of driving. Occurs 80% of the time. Cannot be repeated if you cycle through M 1 and M 2 repeatedly (even immediately after a cold start).
  • Lightly blipping/feathering the throttle while in 3rd gear traveling at roughly 22-28 MPH. Car must be driven for at least 20-30 minutes prior before sound occurs (operates normally before then). Sound is constant rather than isolated if throttle is continually feathered to keep in MPH range. Does not occur in any other gear or MPH range. Occurs 80% of the time.
  • Shifting from 2nd to 3rd and 3rd to 2nd at roughly 22-28 MPH. Car must be driven for at least 20-30 minutes as there is no sound up to this point (car changes gears normally). This is how I initially noticed the sound but it has since grown to incorporate others. Occurs 85% of the time.
  • At cold startup (25% of the time, does not trigger again if you immediately cycle startup)
  • Shifting into 1st gear from a stop - Recent development. Car must be driven for 20-30 minutes (car changes gears normally up to that point). Occurs 50% of the time

Sound Captures:
  • Exhibit A - captured while switching from M1 to M2 (car stationary in neutral)
  • Exhibit B - taken while driving with a friend
  • Exhibit D - moving away from the camera
  • Exhibit E - shifting into first gear to make a turn

Misc. Characteristics
  • No CEL tripped
  • No leaks
  • Dealership has ostensibly checked the engine bay and found no issues
  • Outside of the noise occurring in more frequently (and spreading to different aspects) the car operates normally
Instances where the noise is triggered by the clutch:
  • No loss of drive train power
  • On clutch being released
  • Clutch pedal is not sticky in its range of motion

The noise is not the...
Here's what I can rule out:
  • Clutch pedal - this can be moved in and out freely at any time (car on or off) without noise
  • Interior cabin - the noise occurs when the car is stationary and I'm intimately familiar with all the rattles.
  • Brakes - I have CCBs so I am acutely aware of the unearthly squealing they create while being applied.
  • Any manner of timing belt - Timing belts are a very distinctive sound and this not it.

Could it be...
  • The clutch - I initially believed that this was the primary culprit as the noise occurred first while switching between 2nd and 3rd gear (both up and down shift) at the specific MPH range. But why not in any other gear change (say 4th to 5th?) or any other speed?
  • The throttle - I'm now suspecting that this may be the issue due to the recent development of the sound being triggered by switching between M 1 and M 2 after being driven for 20-30 minutes. Also, lightly blipping and feathering the throttle while in 3rd gear travelling at 22-28 MPH and having the sound constantly occur over a prolonged period leads me to believe that it is not the clutch as the vehicle is already in gear. But if it's the throttle, then why doesn't it occur in any other gear or speed?
  • Suspension - the noise sounds an awful lot like a squeaky suspension but then again if that were the case, it should occur constantly, regardless of gear, speed, and quality of road surface rather than the specific 3rd gear characteristic.


Once again, any help that can be provided will really help me out as I'm at a complete and total loss what to do. Thanks again!
So, what's the diagnosis?
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