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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Wed, Sep-12-2018, 10:47:12 PM   #1
CarbonVert
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Default Rear end clunk only when cold?

Hello,

Recently I noticed that I have a rear end clunk when the car is moving and I lightly apply throttle. It sounds like it is coming from directly below the rear seats.

5k miles ago I replaced all my diff bushings with ECS poly bushings (I wouldn't recommend them). During the install I looked and couldn't find any subframe cracks.

The weird aspect of this clunk is that it only occurs while the car is cold- after 10min of driving the noise is gone.

My question is can the amount of play in a diff change as it heats up?

Thank you for any insight
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Old Thu, Sep-13-2018, 12:03:33 AM   #2
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Default Rear end clunk only when cold?

Front differential bolt is your likely issue. It requires quite a lot of torque (153ftlbs?) to keep it from moving. Maybe yours is just about tight enough so as heat builds up and expands metals, that diff bolt movement is tight enough not to clunk.

Itís pretty easy to get to. Just remove two or three screws holding in the plastic cover to have space for the torque wrench to swing.

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Last edited by rovert604; Thu, Sep-13-2018 at 12:12:47 AM.
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Old Fri, Sep-14-2018, 10:05:56 PM   #3
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Default Re: Rear end clunk only when cold?

I got under the car yesterday- the front diff mount bolt was extremely tight.

What I did find was that the v-brace bolts were loose. Based on the torque specs they are stretch bolts that I will need to replace. But just torquing them down further now significantly reduced the clunk.

Not sure why this would cause it to only clunk when cold but I'm happy to resolve the issue.


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Discussing Torque Spec thread in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)