E46 M3 Differential Removal Guide | M-Clunk, Differential Bushings & BMW M3 9-Year Ownership Update
In this video, I give a brief background on my 9-year E46 M3 ownership experience, including the key maintenance and modifications I've done to this M3. I also describe the symptoms of M-clunk and the long-term issue I am having with the M3 differential which has clunked badly for a long time.
Spurred on by a diff input shaft leak, I am finally taking the dive and investigating the problems with my diff with a view to solving them.
Here's what I used in this video:
E-Torx Spanners: ebay.us/LAkQFk
E-Torx Sockets: ebay.us/YPEsBZ
Dewalt 18v 3/8 Ratchet: ebay.us/Wk14qg
First thing to cover off is that E46 M3s are notorious for their clunky diffs, they almost all have this issue and luckily it's not as bad as it sounds. It can be caused by a few different things including the fundamental design of the diff meaning one of the splined output shafts is shorter than the other, allowing for wear and movement leading to a clunk when picking up drive.
Another common cause is worn-out diff bushings. When I sent this M3 off to ETA Motorsport for the RACP boot floor reinforcement, I asked them to fit Powerflex bushings to the diff, thinking it would solve it. Unfortunately, it actually made the clunk far louder, to the point where passengers turn to see who just gave us a rear-end shunt when I change between first and reverse in a car park.
In time, I learned to live with it and drive around it, to the point where it no longer bothers me so much, especially understanding that there's nothing seriously wrong with it, just a quirk of the E46 M3. However, it taints an otherwise lovely example, and I know if it ever came down to sell, the diff would seriously put off the type of buyer I'd want to attract to this car.
With the new addition of a dripping input seal, it's time to remove the diff and investigate the clunk while I am resealing it.
In the recent past, I was fortunate enough to purchase a second E46 M3 differential which is supposedly in good condition and working well. So I have a second diff on the shelf which I can compare side by side to my original before deciding which to refit. I noticed the new diff also has an input seal leak so either one needs that replacing (in an upcoming video).
Removing the differential from an E46 M3 was actually more challenging than I anticipated. I am now spoiled by working on the E30 which is an older style car, not as tightly packaged or complicated, and with space to actually get your hands in to work.
The E46 M3 is at the turning point where cars started to get harder to work on, and everything is in the way of everything else. Thus I had to remove undertrays, the rear anti-roll bar, heat shields and even the whole exhaust from the manifold back to get the access required to drop the diff.
Once all that was out of the way, I could start work removing the diff, firstly I worked my way around the E12 e-torx bolts holding the driveshafts to the output flanges on the diff. This is where the job took a turn for the worse.
One of the half shaft bolts rounded off on me, so after some fighting, I had to use an angle grinder to cut the head off the bolt to be able to continue.
With all those out, I then removed the prop shaft bolts which came out sweet due to them being less corroded.
That left me with the three main fasteners connecting the E46 M3's differential to the rear subframe. The front and very large bolt is a 21mm head, and should be in good and tight with a 200nm torque spec, I got mine moving nicely with a breaker bar.
My rear diff bolts were hex head Powerflex items which are nicely accessed using a ring spanner, OEM bolts are E12 E-torx and can be difficult to remove thanks to the shape of the boot floor preventing you from getting a socket and a ratchet in. Although it can be done with patience and pragmatism.
Once all the bolts were out, I found my diff to be still stuck in place despite giving it a good jiggle around. With the jack beneath it, I realised there are slots on the prop shaft flange, stick a flathead screwdriver in and twist to release the diff.
Sadly my diff fell off the jack and to the floor, surprisingly with no real damage to the rear cover which was very lucky. You should be more careful, it weighs a lot!
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