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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