Differential Clunk Potential Cause

[Pajarito61906]

Alright so obviously theres many threads here about clunk complaints heard in the rear and many saying its basically normal. I bought my 2015 M4 6 speed 2 years ago with 42k miles and had that issue so i thought it was normal when i would hear that clunk. Well all behold i installed AA midpipes and while under the car i found a crack in the rear differential bushing. I ordered the part at bmw for $130 which took 2 days to get in, then my mechanic swapped it out for $200 and voila the clunk is gone. Im not saying it will be the issue every time but if you encounter this problem this should be the first thing to check. Here are pics of the crack circled in red you might have to zoom in to see it

[NoSuchSol]

Is there an easy way to see if without getting a lift?

[aBMWfan]

Where you located?

[Pajarito61906]

Originally Posted by NoSuchSol

Is there an easy way to see if without getting a lift?

Yes just slide under the car with a flashlight if you are able to fit under it or a simple jack with a jack stand.

[Pajarito61906]

Originally Posted by aBMWfan

Where you located?

Im located in san diego

[aBMWfan]

Originally Posted by Pajarito61906

Im located in san diego

Interesting I'm not too far. Did he have to remove the subframe to access?

[Pajarito61906]

Originally Posted by aBMWfan

Interesting I'm not too far. Did he have to remove the subframe to access?

My mechanic told me he had to drop the exhaust and losen some suspension bolts to be able to drop the differential just enough to get access. He said it was a tight squeeze but was able to do it but i will need an alignment since he had to do that.

[JamesF80m3]

My M4 was clunking from the rear diff at around 60k. I changed all rear diff bushings and there was no difference. I then seen someone online that was changing there rear diff fluid and said that if you dont change it metal particles build up and cause the clunk so doing that fluid change may prevent future clunk.


We also might have had two different clunks coming from the rear

[2011ninja]

Originally Posted by Pajarito61906

Alright so obviously theres many threads here about clunk complaints heard in the rear and many saying its basically normal. I bought my 2015 M4 6 speed 2 years ago with 42k miles and had that issue so i thought it was normal when i would hear that clunk. Well all behold i installed AA midpipes and while under the car i found a crack in the rear differential bushing. I ordered the part at bmw for $130 which took 2 days to get in, then my mechanic swapped it out for $200 and voila the clunk is gone. Im not saying it will be the issue every time but if you encounter this problem this should be the first thing to check. Here are pics of the crack circled in red you might have to zoom in to see it

Originally Posted by Pajarito61906

Alright so obviously theres many threads here about clunk complaints heard in the rear and many saying its basically normal. I bought my 2015 M4 6 speed 2 years ago with 42k miles and had that issue so i thought it was normal when i would hear that clunk. Well all behold i installed AA midpipes and while under the car i found a crack in the rear differential bushing. I ordered the part at bmw for $130 which took 2 days to get in, then my mechanic swapped it out for $200 and voila the clunk is gone. Im not saying it will be the issue every time but if you encounter this problem this should be the first thing to check. Here are pics of the crack circled in red you might have to zoom in to see it

Awesome you took the time to share information and photos.

[hC1001]

Originally Posted by Pajarito61906

My mechanic told me he had to drop the exhaust and losen some suspension bolts to be able to drop the differential just enough to get access. He said it was a tight squeeze but was able to do it but i will need an alignment since he had to do that.

For $200, thats a steal. Im hoping to tackle this job myself and finding the easiest way possible. Replacing with powerflex bushings for ease and durability. Very hopeful to hear your mechanic was able to replace the bushing with minimal disassembly.

As another data point, I do not have any clunking from the rear end and my bushing looks worse. It has two tears in it on opposite sides. Wouldnt have known anything was wrong if i didnt visually inspect it.

[NoSuchSol]

Going in tomorrow for service - I replaced my steering wheel today so while I had the garage open I hopped under. Mine was damaged in the same place and had some fluid around the other side.

[Pajarito61906]

Originally Posted by NoSuchSol

Going in tomorrow for service - I replaced my steering wheel today so while I had the garage open I hopped under. Mine was damaged in the same place and had some fluid around the other side.

Woah your bushing was all tore up, good thing you went under to take a look. I bet many people have this issue and dont know it.

[Jbonly21]

Originally Posted by HarrisoneliF82

My M4 was clunking from the rear diff at around 60k. I changed all rear diff bushings and there was no difference. I then seen someone online that was changing there rear diff fluid and said that if you dont change it metal particles build up and cause the clunk so doing that fluid change may prevent future clunk.


We also might have had two different clunks coming from the rear

I just did my diff fluid at 55k , and I was surprised how much metal shaving was in it. If you are over 40k, you should differently think of changing your fluid. And to Op good find on the bushing.

[NoSuchSol]

Originally Posted by Pajarito61906

Woah your bushing was all tore up, good thing you went under to take a look. I bet many people have this issue and dont know it.

I'm a little perturbed with the dealership about it - I have had a metal pinging noise in the back of the car since I purchased it. They've been around that car a few times (replaced brake shields and such) so I'm surprised they missed it. If I can see if without a jack then shouldn't that be able to do a physical inspection easily when they're already working in that area?

Otherwise, they've been on point and always happy to try to help. A bit different than the last dealership I had to work with.

[Crums440]

Sorry to dig up this thread, but i also am getting ready to replace the rear diff bushings with powerflex, and am finding that the best way may be to drop the exhaust, and lower some part of the subframe to get access, according to most the posts. im trying to avoid removing axles, and dropping diff completely out. any tips?