550i clutch upgrade: complete ✅
18 hours of work later, and my 340i 6MT has a brand new clutch, the 550i clutch that can hold ~100hp more than the stock version. Knowing what I know now, I think I could do the job in less than half that much time, perhaps in a single day (less than 8 hours) if I got started early enough. But for this first time around, I took my time and tried to enjoy the process. This is only the second major car work I've ever done in my life after brakes and rotors last fall, so it was like jumping into the deep end of a pool and learning how to swim. But I just took it slow, and MAN what a blast this was.
First, HUGE thanks to
kern417 and his video on replacing the clutch in his 440i, which is the same process for my 340i:
https://youtube.com/watch?v=9cwJV5SKl40. I'm not sure I would have attempted this without the work he did to document the process. Second, I was very much assisted by the
BMW TIS guide on how to replace the clutch. Those two guides alone got me 99% of the way. I just needed a few odds and ends otherwise, like how to use the clutch alignment tool and how to bleed the slave cylinder.
That said, there are some things that Kern417 did in his video that I think could be looked at. A minor but important one is to mark on the driveshaft with a white paint pen where it originally was connected. This way you reattach it back how it was and avoid the chance of vibration after the repair is over. The biggest difference between me and Kern is I feel that
a transmission hoist is pretty much a requirement for this job. I know Kern bench-pressed the transmission into the car and then tightened the transmission bell housing bolts, but not only is that near impossible for most people strength-wise, it's also very dangerous considering you have a 100 lb transmission precariously balanced above your body with no real leverage for protecting yourself if it comes crashing down. For goodness sake, spend the $129 + tax at Harbor Freight like I did and get a mini transmission hoist so you can get that massive hunk of metal up and down without major risk of injury. The hoist can be reused for dropping and installing the exhaust as well.
Some reflections:
- It is amazing how much work is required to get this relatively small clutch disc into your car. It requires removing your underbody panels, entire exhaust, heat shields, disconnecting your driveshaft, and then finally you have access to the transmission bell. Once there, getting at the bolts for removal of the trans is quite challenging, especially if you're like me or Kern and you're doing this on jackstands with less than 20 inches of space under your car. But with enough patience and socket extensions, you can get the bolts out and wiggle the transmission off the engine block and onto your transmission hoist. Then you lower the trans to the ground and slide it out from under the car. Then remove the clutch pressure plate and clutch, and examine your flywheel. Depending on the flywheel, you may need to service or clean it, or remove it and have a new one installed, or remove it to have it resurfaced. Then refresh all the various hardware in the transmission bell. Then you just do everything in reverse... you slide the trans back under the car, get it back on the hoist, jack it up to your engine, and reassemble everything. It's a huge process. But wow, it was so enjoyable.
- My favorite moment was getting that transmission bell back onto the hoist while under the car with 20" of vertical space. I spent over an hour trying (and failing) on that. I couldn't figure it out and was a little scared I would have to call a tow truck and have it done by a real mechanic. But eventually I realized that I could slide the transmission up from between my legs onto my chest, then move the hoist between my legs, and then slide the transmission back down my body and onto the hoist. Victory!
- Halfway through the job, I realized why my car had been throwing drivetrain errors about not getting enough torque on the clutch. As I removed the clutch pressure plate and clutch, the car's flywheel was revealed. It was covered in a moderate amount of surface rust. Thankfully, the rust had not pitted the metal of the flywheel, so it could easily be removed. I spent about 2-3 hours patiently polishing the flywheel with plastic low-abrasion polishing bits to get that rust off (mostly failing). Finally I resorted to 2000 grit sandpaper. I know the flywheel needs to remain with an evenness of 0.004 inches across the surface, so I made sure to lightly sand with 2000 grain sandpaper to the point where I did not remove the machine grooves from the surface of the flywheel. In the end, I'm fairly happy with the result. 90% of the surface rust was removed from the flywheel and the machine grooves on the flywheel were still there, which means the flywheel was (probably?) still within that 0.004" flatness. I was on the verge of ordering a new flywheel at first ($1300), but in the end I kept it in there, and I'm glad I did. If the clutch still throws draintrain errors, then I'll get back in there and simply install a new flywheel. But for now I think my surface polishing did the trick. I'm still confused how the flywheel got rusty. I noticed water stains on the floor of the transmission bell, so I wonder if somehow the transmission go flooded by a previous owner.
- I am glad I pre-ordered replacement parts I might need for this job. For example, I had replacement bell housing bolts in case I rounded one off on removal (I didn't use them, so I will return them for a full refund). Most helpful to have on hand were the replacement clutch pivot pin (brass instead of plastic), new guide tube, new release bearing, new release fork, and new spring clip. The fork and bearing comes with the 550i clutch disc, but the guide tube, pivot pin, and spring clip I ordered separately.
- Aligning the clutch was a bit tricky as I'd never done that before, and Kern didn't show how to do that. But with enough Youtube videos of other people doing it, I figured out how the tool worked, and my clutch was aligned.
- I was excited to do my CDV delete and get more clutch performance, but upon getting into it I realized the CDV had been deleted by a previous owner. Learned something new about my car.
- Finally, Kern says in his video "Oh yeah make sure to bleed the slave cylinder", so I just assumed that bleeding the clutch would be easy to learn. Well, it was actually a bit tricky. In trying to bleed it I accidentally introduced a ton of air into my slave cylinder. I had to order a Motive power bleeder and wait 4 days for it to arrive. Then spend another few hours learning how to bleed my brakes and clutch. In the end, I was successful, and my car now has new brake and clutch fluid, which it needed anyways.
In the end, the clutch got replaced, the transmission got hoisted back up in to the car, and after all the stuff got bolted back on (after bleeding the slave cylinder) I was able to drive the car around. I checked ISTA and the car is throwing no errors. I'll do my 300 break-in miles to get the clutch fully seated, and then I look forward to seeing if this 550i clutch can hold the 450hp that BM3 stage 2+ can offer. The 550i clutch seems capable of 500whp so 450whp shouldn't be too much of a stretch.
All in all, I highly recommend people take a few days off and challenge themselves to replace their own clutch. This might sound a bit cheesy, but not only did my sweet 340i get a clutch upgrade, but I also grew as a person. After heaving around that heavy transmission bell, getting it all serviced with new parts, and getting it back into the car, I feel a ton more agency as a man, more power to exert my will upon the world.