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Discussion Starter #1
Having a loud clunk in the rear end when shifting hard, the harder you shift the harder it clunks, at WOT you can feel it hit and it sounds like someone in your trunk kicking the back seat.. ( wait did i leave the wife in there? lol nope double checked )

It also appears to be getting louder and firmer as time goes on . was under the car today nothing appears to be out of place..

Any ideas, its not coming from the trans 100%, its definitely in the rear of the car, its not a quick clunk like a gear sound, its more like a thud or a hammer hitting the floor. I looked for broke mounts but dont see anything, I might have to get the wife to cycle the gears while im back there looking.....

While reading up on the bmw clunk i see lots of older bmw with broken mounts back there but nothing broken as far as i can tell..

Was wondering if it might be the the rubber mount points getting worn out.. anyhow im out of ideas..

Let me know what you think ..
 

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Discussion Starter #3
It happens with any of the shift settings , if you shift really softly with out laying down a lot of TQ you dont notice it..
 

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Check the diff mount bushings (front and rear) 2 on front, 1 on rear. If they're good, check the diff cradle mount bushes. If that doesn't work, check the diff play. With the car in the air, hold the wheels and check how much diff play you have turning the drive shaft. When I did that, I found my knock so I replaced the diff. I couldn't find anyone that could help tell me how to tighten the clearances or adjust the pinion lash so I opted for a replacement. You may have better luck but there seems to be a genuine shortfall of knowledge about the rear diff's inner workings and how to adjust.
 

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I had the same issue. It turned out to be the rear differential/ bushings. I replaced the entire differential and the beast is running as hard as ever.
 
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