2011 E70 35D Strange sound when decelerating
 

I've been a long time lurker now a first time poster.
My 2011 X5 E70 35D started making this strange sound when decelerating. The vehicle feels like the brakes are being tapped and applying the brakes doesn't change the sound or feel.
Here's a short video of it.
https://www.dropbox.com/s/gazbv3z8kl...200_1.mp4?dl=0
There are no CELs or codes. Recently tuned and deleted.
Any help would be appreciated.
EDIT: Used Foxwell Nt510 and got the following codes: A0B3 CF37 5DCF 6EC4 55C3 55D0
I am leaning towards the transfer case actuator motor gears.

I would eliminate abs system from the equation by disabling it. Unplug the right fuse will do it else pull the connector on a wheel speed sensor.

It sounded very periodic at one point and that points toward CV joint. Are you just engine braking or actually hitting the brakes also?

At one point it also sounded like bad sway bar links but that's not periodic sounds more like Morse code.

Not pressing the brakes, just coasting down. Thanks for the reply, I'll check those items out.

I inspected and road tested these items and they are good to go. I also pulled all 4 wheels and inspected the brakes, nothing. I am going to pull the transfer case actuator motor and inspect the gears and service the transmission this week and go from there.

It sounds a little like when the front find shaft slips in e53, but I believe e70 is bolted on but the sound is also similar to stripped TC actuator though usually when those strip you hear the clicks when you turn off the car.

I serviced the transmission and transfer case, small metal flakes in the TC fluid, and replaced actuator gears even though the old ones had little wear. Front drive shaft has a little play. See this video:
https://www.dropbox.com/s/iymcuvv4vk...24326.mp4?dl=0
Pulled fuse for TC, went for test drive and had same sound when decelerating, however, when I gave it just a little throttle while braking, the sound went away.
I'm going to pull the front drive shaft next and go from there.

With TC fuse out, the front drive shaft will be "self propelled" from the front wheels. The disconnect is "upstream" of the TC > front propeller shaft and the sound does sound like the prop shaft slipping. I thought they fixed that problem with e70.

When engine braking power will be transmitted via prop shaft and TC.

I think I would be pulling the front prop and take a look at the spline.

I can't remember what it takes to remove/replace but I did on 328xi and I think it's very similar. I think I would pull the front prop and confirm if 1) splines ok and 2) will sound go away.

Theory is: spline slipping when engine braking. When you add throttle the TC guts catch up. With TC fuse pulled the clutch won't engage but parts still spin and offer some slight power transfer.

Pulled the front drive shaft and test drove, still same noise, goes away with just a little throttle. Splines and u-joints look good, no play. With there being metal flakes in the TC oil and the 55C3 code, I guess I'll pull the TC and see what's going on in there. Not looking forward to it.

That is progress: it's hard to imagine freewheeling dif making the noise. If you said you got metal chips in your TC oil I can't imagine some way it's not the source of the problem.

Any news?


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Pulling it tomorrow. Got side tracked helping my son get his RV ready for his lower 48 road trip.

Generally (I know you have been through a lot of this) when decelerating causes a noise, it is the pinion bearing. Maybe this helps you with investigation.

I'm not familiar with the pinion bearing. I rechecked the wheel bearings, control arms, sway bar, engine mounts...everything appears in order.
Pulled and opened the TC and nothing stood out as damaged. Chain and gears look good, very little slack.
TC video:
https://www.dropbox.com/s/r4305m0eta...551_1.mp4?dl=0
I did damage the TC case because I neglected to remove the output shaft flange before popping the case open. I found a used ATC700 on Ebay so I'll install it when it arrives.

I did the same on customer old case I wanted to do post mortem couldn't figure out how to open non destructively and I own a bandsaw.

I've not heard it going fast but it's almost identical to loose guibo bolts. Have you looked at guibo/s?

My customer 328xi would make almost the exact sound in forward when creeping (eg drive through). It would even only some of the time do it.

I had to change his TC and when I did I torqued the bolts and vaporized the clicks.

His car the guibo goes to back but yours should be in front.

Pinion bearimg
 

It may be called differently in BMW but is the bearing where driveshaft enters differential.

Ahhh... ok. I'll check that out later this week. Working on son's MB diesel RV for the next few days, just maintenance items.
Thanks for the info.

The guibo looks good, no cracks or deformities, and the bolts were very tight. The mid shaft bearing looks practically new as well.
This is bumming me out because I really want to get out and enjoy the new 2.5 tune.

What is "very tight"? They def need to be torqued to spec.

The tick is from metal to metal motion nothing to do with the rubber condition.

I tried to just snug the guibo, and tick still existed. The tick disappeared when I had to disassemble and re-install all the n bolts.

Just based on how close that sound reminds me that's my prime guess

2011 E70 35D Strange sound when decelerating
 

https://youtu.be/yx9nCMKeIdw

Take a listen to a loose guibo bolt situation. Was yours taken apart and reinstalled? It's important to get the bolts the correct way and some use washers also critical.

Reused bolts can also throw off torque application and have the bolts not be tight enough.

My torque adapter is too large to fit in there so I need to use wobble extensions to get in there but it's important to torque to spec.

Use the likes of GoPro if needed to video while driving.

Persistence pays off you'll find the sound source and solution.

It's possible the sound is a shield getting hit by a rotating part that only happens from flex under engine braking. Look for things that are close to the drive shafts and telltale rub.

Also do some math:.

In the beginning of the video there is a very repetitive sound. Like tap tap pause tap tap pause.

Figure out the milliseconds between the pauses and you can calculate the frequency.

Recreate at a known speed. The differential is 4:10 or 3.91 : you can determine the rpm of the driveshaft and if it's a match it's drive shaft related even if pinion inside dif.

https://youtu.be/m78p41HBE-8

https://uploads.tapatalk-cdn.com/202...0a2b225995.jpg

Important detail of guibo install

https://youtu.be/Vw7Zbp1rfGI

Loose shields and/or panels was my very first thought since I had removed most of them to install the new downpipe and mid pipe. Nothing had rub marks and and pieces were clear from moving parts.
I had to use my 1/2" breaker bar with some "umph" to loosen the guibo bolts and the guibo was was facing the right way with the bolts placed properly.
I did find 1 motor mount bolt not seated all the way and I can't specifically remember torquing the subframe bolts when I buttoned everything back up.
Of note, I live down a 1/4 mile gravel road and it doesn't make the noise on it.
So my replacement ATC700 will be here Friday, I'll get everything back together and test drive with the gopro mounted in various locations and go from there.
Thanks for all your input and links Andrew.

100% chance to track this down. XO rarely ever fails.


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Alright, got everything put back together and torqued to spec, the subframe was already torqued from dpf delete. Still getting strange sound, but I noticed that the engine has to be warmed up for it to happen and the RPM fluctuates with the noise. I shot video from various spots around the engine to try to pinpoint the origin.
https://www.dropbox.com/s/jrod2nyoq0...sound.mp4?dl=0
When I did the delete I replaced the thermostat and also did a swirl flap delete.
I'm still learning how to data log with my Foxwell NT510.

That is one of the craziest things I’ve ever heard. You need to use an app like FFT to figure out where the sound is coming from because it will measure not only in the sound pressure level but all the frequencies related. You can definitely figure out for example is it coming from the left or the right of the front or the back.

Also use the vibration app determine the exact frequency of those clicks you can also just use an app audacity To look at the way for him and measure the milliseconds between those clicks.

We can determine from the speed of the car where are the sound is coming from based on the revolution in the drivetrain.

Is it possible that some thing controlling the turbo wastegate or boost Is somehow clicking open and close.

Perseverance is going to pay I promise. It’s way too obvious in way to repeatable that we can’t find the problem

Agree with andrewwynn, that is really quite something. Definitely not a pinion bearing issue, now that I hear it. The tapping, at first, sounds somewhat like a spark arcing or exhaust leak tap. Listening to the video (at watching what little can be seen) does not lead me to believe it is RPM related, unless it is in combination with speed and flex from acceleration /deceleration. It seems most to me like exhaust tap, as above could be turbo related possible EGR. Quite loud to be an internal noise, leaning towards leak somewhere. Curious indeed, quite frustrating I am sure.

Need to determine if the sound is in sync with the engine or drive train.

I'm thinking that is a rotating part contacting a heat shield.

Imagine a bolt from flex disc but just two of six hitting;

Tap tap pause pause pause pause tap tap then after a while three hit so it's tap tap tap pause pause pause.

The engine braking just putting torque on the motor to move things around.

Check the mechanical fan of your engine has one. I've seen it happen when engine torque moved the fan enough to contact the shroud and the sound of each blade slightly hitting the shroud was similar. (though this sounds more metallic)

Thank you andrewwynn and 13brian for your input.


Here's where I'm at so far:
The sound appears to be coming from the passenger side front near turbo
No mechanical fan
Happens at all speeds and RPMs

No DTC's or CEL's
It doesn't happen until engine is warm
Only happens when decelerating and goes away with slight acceleration
Not the waste gate
Not the transfer case or drive line

Didn't have this sound before EGR, swirl flap, def, dpf delete with 2.5 tune and VRSF downpipe. I replaced the thermostat as a prevention.
Other than the noise, it runs great. Drove 40 miles last week and just 2 footed it.
Going to do vacuum testing next week. I already replaced most of the vacuum lines last week.
Really stumped.

A couple thoughts:


1) vs. a little throttle, does putting in neutral stop the sound

2) it's reminding me of Jake brake just intemittent and softer and higher frequency than a semi.

Does your engine have exhaust braking? I could not find reference yes/no online.

3) intelligent alternator control; the alternator is supposed to charge "only when braking/coasting"; if the alternator is kicking on/off a surge of force related to this could be causing motion that is causing right a physical tap or a surge of current can cause wires to slap.

Putting it in neutral does make the sound go away. (Just tried it.)
No exhaust brake.
Turning DSC off/on makes no difference.
Not sure about the alternator. No spikes shown on the Foxwell.

Make another recording at an exact speed and tell me the speed.

I can determine if it's drive train or not with some meausuring and math.

Not long ago I determined a similar mystery sound was exactly 3x wheel rpm which led to thinking CV axle (inner joint has three lobes).

If we can find a part that rotates at a similar rate it may determine the source.

Do you have any universal joints or just guibo? A recent thread showed a u-joint disaster that grenaded and blew out the side of the block. We want to rule that possibility out before it happens to you