545i Rear metal/metal clunk on acceleration
 

Hey guys so car has about 160k and when I accelerate very slowly you can hear this clunking/creaking metal to metal noise in the rear end, basically it does it any time the car shifts weight, so like when going 5mph and slowing down it does it. It's an SMG 6 Speed Manual and it doesn't do the sound if the car is in neutral ...only when in gear and jerking back and forth with the clutch will make it go faint clank clank clank like plates hitting eachother. Any ideas? Nothing in the rear suspension has been replaced honestly I don't think probably ever so it could use some bushings I guess lol?

There's a splined slip joint in the driveshaft. Could be dry.

Did you ever figure this out? Have the exact same thing going on with my 545i 6-speed manual.

Can you duplicate the noise when stopped and have the hand brake set? Load the drivetrain in first and reverse?

Get the car up on ramps, then grab the drive shaft and turn it back and forth by hand, listening for noises. You may also want to try the center joint area if it's accessible.

I have only noticed the sound when moving off or slowing down from an already low speed. So if I'm in stop-and-go traffic, you will hear the sound with every change in acceleration or deceleration that causes the weight to shift. At first, I thought it was the engine mounts but recently learned that the sound was actually coming from the rear. I'll try loading the drivetrain with the hand brake set and see if I can duplicate the sound. I'll also get the car up in the air within the next few days and try your other suggestions. Thanks.

My manual has the same issue and it is kind of embarrassing at low speed. Every time I left off the clutch it starts to clink/ping/ring or a quick lift of the throttle - anything that load or unloads the driveshaft. There is a small note in the Bentley manual about greasing the input shaft in the differential as audiophool mentioned. Only problem is I don't have the time to pull the exhaust to drop the heat shields to get in there. Keep us posted!

Nothing seems amiss with the driveshaft. The center support joint seems fine and I could not recreate the sound from turning the driveshaft back and forth or by pulling on it in a few directions to check for looseness. I'll get back under the car this weekend and fiddle with the driveshaft some more before totally ruling it out. I will probably also replace the giubo and center support anyway since I am this far in. Stay tuned.

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