Noise in rear end

I have a 2004 BMW 330XI. For the least few months, when traveling 65mph or more, I am hearing a whump sound in the rear end which happens when I am excelerating after decending a hill and starting up another. When I say hill, big or little, it doesn’t matter. However, it may happen 3 to 4 times in a matter of a few minutes and then not happen again for 30-45 minutes. There have been a few times when I’ve been on a rather even surface and it’s also happened when accelerating.

Thanks. Hope someone can help!

I would guess that the BMW people have heard of this one. The differential may be binding and releasing violently (guessing, don’t know). Fluid needs checking at the very least.

Check the drive shafts and joints too…

i would investigate the rear shocks. looking for a broken shock or shock mounting bracket.

also the rear axle springs should be checked for a broken slipper bracket too.

these things should be on any mechanics list of stuff to check given the description.

Could your noise be related to some major component replacement,or accident damage. A good visual inspection that includes putting a wrench on every bolt you can access could get you closer to resolution. i have a tech source and will check for you will post latter (not tonight)

Does it have to involve a hill, could it happen if you de-accelerated & accelerated on the flat or woung over a hill ranther than a hole?.

Could it bea loose fuel tank, where is the battery in this, front of Trunk?.

Ths one had an floating differential housing I imagine, is it secure in it’s mountings

Could just be the slack in the pinion/ring gears in the rear axle. As you’re coasting the rear axle is rolling with the tire speed and the drive shaft is idling along with the engine at ALMOST the same speed. As you begin to accelerate the two are playing catch-up with each other creating the noise.

Drive shaft and u-joint(s) would be my best guess also.

Thanks for your input. The dealer has had the car for three days and has found nothing. I’m picking it up tomorrow. Don’t know what all they looked at, but plan to find out.

I’m picking up the car from the dealer tomorrow, after three days and nothing found! The car was in an accident (front end), when I had only had it three months. Thanks for input. If you have anything further, please let me know.

Thanks for the input. Dealer has had the car for three days and told me to pick it up tomorrow. They couldn’t find anything.