I had an awful noise begin 2 drives ago in my 240d. I noticed a clunking/grinding noise only on higher rpm's in 1st gear.

It would make 3 clunking noises, then after I'd shift into second, it would stop until I'd get into higher RPM and then it would clunk/grind many more than 3 times. The sound was accompanied by intense vibrations.

I found after that drive that the air filter housing had broken off causing a horrible rattling, and I identified the noise with that.

After mending the air filter housing, I drove the car again today and the same clunking/grinding noises and vibrations were apparent, and began worsening.

The grinding in second gear became almost constant and more intense, causing the car to jolt back each time the sound occurred. It disappeared while accelerating and cruising in 3rd and 4th gear, but in lower rpm coming to a stop in 3rd gear it would ensue around the 25
It sounds like it's either coming from the rear end or more under the drivers seat at the driveshaft.

A friend of mine has suggested to me it sounds like the differential, but also told me to check my axles and driveshaft.

I replaced my passenger side rear axle earlier this year where it sounds like it may be coming from, but i think it's also noteworthy to mention the flex discs are cracked all to hell. I already have replacement discs and driveshaft support + support bearing, just haven't put them on yet because I've been so busy fixing other problems she has been throwing at me.

What does it sound like to you guys?