Rear End Clunk Woes

[moproblems]

Hello,

I have an 04 SMG that I have been fighting a rear end clunk (almost a bang) for a while, it's coming from the rear somewhere and I can't seem to find it. Happens low speed when pulsing the throttle, on shifts with the SMG especially at high shift settings. You may think it's diff bushings, well, so did I. I have replaced:

• RTABs (Monoball)
• Diff bushings
• Subframe bushings
• Guibo
• CSB
• All other rear bushings
• Installed Vincebar and lower plates

I inspected the diff when I did seals and didn't notice anything abnormal. Driveshaft CV did not visually have play when pulsing the car with the ebrake on while still making the noise. I need to get it up in the air and see if it's a bad CV on an axle and if it's not that I'm going to guess it's the differential. Is there anywhere else historically I should look at, or just any ideas? I am currently stumped.

[sapote]

I'm going to guess it's the differential..

I agreed that I also think it's the diff.I think if you remove a few clutch disks off the LSD to make it's an open diff then the noise will be gone. The loud clunk caused by the sudden slipage of the LSD clutches which caused the spider gears hit the side gears hard.

[moproblems]

I agreed that I also think it's the diff.I think if you remove a few clutch disks off the LSD to make it's an open diff then the noise will be gone. The loud clunk caused by the sudden slipage of the LSD clutches which caused the spider gears hit the side gears hard.

It's interesting that it happens almost all the time, not like normal m-clunk where it's low speed. I could maybe replace the plates as a stopgap until I save the money for an aftermarket LSD.

[Ramage]

moproblems You might want to check the differential bolts if you haven't already. There was actually an official update/superseded part number for them https://nam3forum.com/forums/forum/m...-bolt-question.

I replaced mine back around 2014, and it made a huge difference in reducing the 'M-clunk.'

[xansabi]

This happened to me as well, clunking and almost banging when pulsing on the throttle, and I didn't even bother going in sport mode. I really recommend using the updated front (from RE) and rear (OE BMW) diff bolts. Super easy to do, the clunking from the pulsing is gone. Sport mode is great now, too. Just follow the thread that Ramage sent, and you'll be golden

[moproblems]

moproblems You might want to check the differential bolts if you haven't already. There was actually an official update/superseded part number for them https://nam3forum.com/forums/forum/m...-bolt-question.

I replaced mine back around 2014, and it made a huge difference in reducing the 'M-clunk.'

Already done. All hardware is the updated part numbers, and all are still torqued to spec. (I actually just verified torque on the diff bolt today as that is what I was thinking too) The only parts not replaced in the suspension are the spring arm inner bushings, which are not torn and look just fine.

I after driving it a bit more it will make a loud thudding/bang when you load and unload the driveline vigarously (think pulsing flat to the floor and then off throttle) just like it does when shifting in either mode 5 or DSC off mode 6 1-2 or 2-3. If I had to guess it's either worn splines/loss of preload (v1 diff) or something whacky going on with the driveshaft CV. Differential is still locking and will still leave nice parallel lines with launch control. Either way I'll continue to drive it, I figure if it's really bad whatever is causing it will eventually break.