Whump in rear end - 2004 BMW 330XI


#1

What would cause a whump in rear end when accelerating after coming over incline? This happens at interstate speeds, never at slower speeds. I wrote back in June and got some ideas. The dealer couldn’t find anything. I would like to take suggestions with me when I go in the next time. Thanks


#2

Get the Advisor/Manager to ride with you and demonstrate to him/her what you have to do to duplicate the concern.

The only thing I can think of and it is a long shot, when these cars are shipped when new there are plastic spacers put around the shafts of the shocks, they are to be removed before the car is sold (part of a Pre-Delivery-Inspection) maybe one or more got left on and the suspension is either topping out or bottoming out early.


#3

Be more specific about the conditions under which you hear this “whump.” You say “when accelerating after coming over an incline.” What, exactly, does that mean?

Is this a sharp transition from climbing to level road? Not likely at interstate speeds. I’m having a hard time picturing the conditions.


#4

Sorry, guess I didn’t describe it too well. It’s the transition from decelerating while going downhill, to accelerating on the level road. This is when it happens 90% of the time. It has happened a few times when I’m on level road and just accelerate. Sometimes it only lasts for a second or two, sometimes longer, like 6-7 seconds. It never happens when I’m driving around town at lower speeds, only when going 65-70 or over. We just drove from KY to PA and back, through the mountains, and it happened a lot.


#5

In a 3-series BMW, the only time I have ever heard a sound that could be described as “whump…whump…whump” it was a rear wheel bearing. However, these are usually most noticeable in the morning when the bearing is cold. I have not seen one that was most noticeable after you have driven a while, but anything is possible.

I have never seen a 330Xi. Hope it is not the transfer box.


#6

I think you’re going to have to have a BMW technician ride with you and hear this noise. I though it only happened once, but now it sound like it happens repeatedly.

Whump, whump, whump, for 6 or 7 seconds is not a sound you want to hear at 65-70 mph. I would have this checked out ASAP.

This car is AWD, right? Sounds expensive. Hope it’s something minor. Could it possibly be something moving around in the trunk? Or a broken exhaust hanger?

If it’s happening a lot you should be able to replicate it with a tech in the car.