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