[aperrin1]

Hey all, I have a 2007 X3 3.0 Auto with a very strange sound that I am having a very hard time diagnosing...Its a mid/high pitched oscillating sound that changes in pitch with vehicle speed (not RPM). It is also NOT reproducible in neutral. The sound is not constant, but I have noticed patterns of when it will occur (although it still seems to be random on how loud/often).

It happens the most dramatically while coasting on deceleration, but also while accelerating around 2nd and 3rd gear. Sometimes the pitch is a constant singing sound, and other times it is more warbly and definitely sounds like a mechanical oscillation. Here are some videos

Oct 22 2018:
https://youtu.be/5Y0HPibHsvM

Jan 29 2019:
https://youtu.be/GCtycVz7mB4

The sound started happening shortly after I had my indy (who is amazing) replace the rear driveshaft that was completely rusted, changing the T-case fluid, and changing one of the VANOS solenoids (to clear a code). This made a huge difference in drivability, but it also seemed to have caused this sound.

That work was done in September, and the noise has not gotten significantly better or worse over the past few months. I haven’t noticed a loss of drivability except for a slight hesitation on throttle and maybe some delayed shifting while climbing hills. It is still way better than before I had the driveshaft and T-case fluid done. I really trust my mechanic, but he is stumped on this one too. He thinks its probably the built-in PCV on the valve cover, although hesitant because it is not reproducible in neutral. He said the only way to tell if its the valve cover is to see if it gets worse, because it inevitably would (but it hasn’t).

I had him change the front diff fluid last week just in case, but that didn’t seem to fix it either.So I was wondering if anybody had ideas, or has seen something like this before. Could it be gear whine from the transmission or transfer case? Or could it be that it is the valve cover and the sound is only occurring at very specific engine pressure…

Thanks!

[aperrin1]

Bump, the sound hasn't changed. Does anybody have any ideas?

[englishtom1596]

Hard to tell over a video but i'll throw out a few guesses from my experience.

Tires would be number 1. Mechanic may have rotated them and if they had some light feathering they can cause howling at certain speeds etc. Try rotating them and seeing if the sound changes etc.

Second would be something in the drivetrain. Either trans, diffs or t-case. Could be low fluid or since your mechanic just changed the t-case fluid. The fresh, thin, fluid could be causing the worn gears to howl.

[marlon08901]

Originally Posted by aperrin1

Hey all, I have a 2007 X3 3.0 Auto with a very strange sound that I am having a very hard time diagnosing...Its a mid/high pitched oscillating sound that changes in pitch with vehicle speed (not RPM). It is also NOT reproducible in neutral. The sound is not constant, but I have noticed patterns of when it will occur (although it still seems to be random on how loud/often).

It happens the most dramatically while coasting on deceleration, but also while accelerating around 2nd and 3rd gear. Sometimes the pitch is a constant singing sound, and other times it is more warbly and definitely sounds like a mechanical oscillation. Here are some videos

Oct 22 2018:
https://youtu.be/5Y0HPibHsvM

Jan 29 2019:
https://youtu.be/GCtycVz7mB4

The sound started happening shortly after I had my indy (who is amazing) replace the rear driveshaft that was completely rusted, changing the T-case fluid, and changing one of the VANOS solenoids (to clear a code). This made a huge difference in drivability, but it also seemed to have caused this sound.

That work was done in September, and the noise has not gotten significantly better or worse over the past few months. I haven’t noticed a loss of drivability except for a slight hesitation on throttle and maybe some delayed shifting while climbing hills. It is still way better than before I had the driveshaft and T-case fluid done. I really trust my mechanic, but he is stumped on this one too. He thinks its probably the built-in PCV on the valve cover, although hesitant because it is not reproducible in neutral. He said the only way to tell if its the valve cover is to see if it gets worse, because it inevitably would (but it hasn’t).

I had him change the front diff fluid last week just in case, but that didn’t seem to fix it either.So I was wondering if anybody had ideas, or has seen something like this before. Could it be gear whine from the transmission or transfer case? Or could it be that it is the valve cover and the sound is only occurring at very specific engine pressure…

Thanks!

Hello!...aperrin1...did you ever find out what the noise was? I replaced the rear drive shaft in my 2006 X3 last week and now it has been doing the same whinnying/whistling sound.