[Antique-ace]

Originally Posted by Antique-ace

UPDATE: BMW Service had my car for 4 days to diagnose the rear thump as well as vibration-related intermittent buzzing sound from my center console area.

The dealership ordered a new center armrest and some related parts to correct the interior buzzing sound (which both the SA and tech agreed was very annoying).

They had much more difficulty pinning down the source of the rear thump, which is much more apparent in SPORT mode. They had the tech ride with me in my car so I could point out exactly what abnormal sound I was hearing. (The sound I hear sometimes when I go over a bump is like there is a softball rolling around inside my trunk.)

They also wanted to find another M240ix on the lot so we could drive and compare to my car in terms of any abnormal sounds, but none were to be had. After some discussion with the tech about what other people on this forum have experienced with this rear thump problem and subsequent repairs by replacing the rear shocks and upper mounts, the tech agreed to give it a try and order the parts. He said he really was not certain this would correct the problem, but he was willing install the 2 new rears shocks and upper mounts in the hopes that this would fix it.

I will post an update once the replacement suspension parts are installed on my car (as well as all the part numbers).

FOLLOW-UP:
So the cause and fix for the rear thump remains a mystery... BMW service had my car for 4 days. They replaced the following rear suspension parts.



Unfortunately, this made no discernable difference in the rear thumping problem as the service tech readily admitted to me when I spoke with him directly after he completed replacing these parts. He told me that BMW is aware of this problem and they have a case file opened for it, but so far no cause has been found or has any repair been recommended to correct this problem. He told me that if BMW finds a fix for this problem or issues a TSB he will contact me.

On the plus side, he was able to fix the annoying intermittent buzzing sound coming from my center console by replacing the following parts.