Transmission drop + clutch swap guide

[Escher]

Yesterday I completed an 8-hour long drop of my 2015 FR-S transmission, including a release bearing swap (the whole reason for the job), fork swap, and clutch assembly + flywheel swap. This forum and videos helped a lot with piecing the whole job together, but no one source seemed to provide all of the info needed into one succinct place. I therefore decided to put together my own guide to follow during the job, stealing quite a lot of graphics from other guides admittedly. In addition, many of the guides go through removing the center console to get to the shifter linkage, which is completely unnecessary. I wanted to provide a clearer set of steps for doing it from below the vehicle.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>Here is the link to the guide.<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

Now it can certainly be improved on quite a bit, to highlight some details, but instead I am going to post some lessons learned here:

1. When removing the clutch actuator from the top of the bellhousing, take your time to ensure you only remove the two bolts on the bottom sides. Take your time so that you don't accidentally loosen/remove the reservoir connection like I did, which spills highly corrosive brake fluid all over your engine and will require you to bleed the whole thing since now you have air in the system. Don't be me.

2. The midpipe to overpipe connection experiences a massive amount of heat cycling, making removal of the two nuts securing it often a nightmare to remove. I myself managed to decapitate one of the bolts on mine. Use penetrant and a heat source like a heat gun or blow torch to remove these. I had the heat gun with me but got cocky since the first nut came off easy. Don't be me.

3. There is a rubber boot which covers the entirety of the linkage between the shift knob in your center console and the transmission. This thing was installed by interdimensional beings who discovered the art of small things into smaller things so that they cannot be extracted by mortals. You can try using a heat gun to loosen the rubber and then try and slip it off the linkage enough to uncouple it. I did, and it still resulted in a ripped boot. From my research, it sounds like the number of people who have been able to remove this thing without ripping it floats right around zero. Its sole purpose is ostensibly to protect the linkage from road schmutz, which is certainly a valiant goal. However, this linkage is also protected by your exhaust midpipe, your driveshaft, and the transmission itself. My boot was spotlessly clean, leading me to believe it can survive quite a long time without its glorified condom. But if you feel particularly sore about it, you can pick a lazy day down the road to replace it. I'm actually looking into some more creative solutions which don't require satan's spandex to cover the linkage.

4. The 4 bolts connecting the driveshaft to the rear differential are some of the most heavily torqued pieces of hardware in the entire car. They have to be, vibrating and spinning the full power of your car as they're wont to do. When choosing your wrench and counter-wrench, I suggest choosing your beefiest with as little wear as possible to get the best grip. These are going to take some serious elbow greese. Use penetrant and a heat gun/blow torch as necessary. The absolute last thing you would want to do is strip or decapitate one of these. That being said, they are manufactured from a much higher strength material than your average hardware. Just use common sense and trust what your arms are telling you.

5. Drain the transmission fluid before removing the driveshaft! Otherwise, you're going to be dumping delicious smelling transmission fluid all over your floor and likely yourself. Not only that, but an empty transmission is much lighter, and therefore easier to deal with, than one full of fluid. After removing the driveshaft, take a ziploc bag and a few rubber bands and cover/seal the driveshaft hole, because no matter how well you drain the transmission fluid, some always seems to linger and wants to escape out the back. This is a quick, easy, and effective way to keep the job just a bit cleaner, because once you get your hands into the transmission you're not going to need any extra filth in your life.

6. Support the engine underneath the oil pan before you remove the transmission. By keeping both the trans and engine level, the trans won't be as likely to catch on the lower two index pins or on the key pins/holes as you remove it. Use a prybar on the baffling of the trans exterior, leveraged against the frame or crossbar, to work the width of the trans from the engine as evenly as possible. This will likely take quite a bit of elbow greese. But if you remove the 6 bolts and 2 nuts securing the transmission, and have disconnected the components you were supposed to in the engine bay, and disconnected the shifter linkage and connecting pins, the transmission will eventually work free. Simply put: follow all of the steps, and you'll be mint. Whatever you do, do NOT leverage the prybar inside any gaps you make between the engine and trans bellhousing no matter how appealing it seems. You can blunt the edges of the mating surfaces and potentially cause cracks or other damage.

7. If replacing the bearing retainer cover, be aware that it is secured with silicon gasket in addition to the 7 bolts. There are two tab-like fixtures on the edge of the cover which are perfect to get a flat-head screwdriver into to pop the thing off. For installing the new cover, be aware that the transmission is a very hot environment, so use high-heat rated silicon gasket. I used Permatex Ultra Copper. Follow the instructions carefully, as they direct you to only hand-tighten whatever you've applied it to at first, wait some amount of time, and then torque the rest of the way to spec after. They also suggest not operating the vehicle for 24 hours after application.

8. Do NOT apply any more than a thin layer of greese on the input shaft, or any other spinning components inside of the bellhousing. If the excess greese spins off and into the clutch, then congrats, you have yourself a nice slippery clutch that won't engage properly and you'll be able to hear it complain about it every time you shift.

9. On that note, DO clean your clutch plate AND flywheel with brake cleaner and then do NOT touch them with your oily hands again! Any oil on these surfaces will lead to the exact same problems above, and brake cleaner removes these oils.

10. A nifty trick to remove/re-install your flywheel without having to jam something in its teeth or have someone hold a wrench on the other side of the engine's drive shaft is to re-insert one of the bolts that was holding the pressure plate in. You can then leverage a wrench in between this bolt and any others around the flywheel to keep it stationary while you torque/untorque. Also, when you are removing the flywheel, be aware that the only thing holding it on is the 6 bolts. Without them, it falls on your head. There's a few mm of bearing that can support it somewhat but it's absolutely nothing to bet exposed skull on. Keep the top bolt for last so it doesn't try to swing over, and as you remove that last bolt, keep your hand firmly pressed to the face of the flywheel. These things are a lot heavier than they look.

11. DO use your clutch alignment tool, otherwise you're going to be slamming the input shaft into misaligned parts of your clutch plate as you try and re-mate the transmission to the engine. Leave that tool through the clutch plate and into the flywheel pilot hole all the way until you have torqued the pressure plate to spec.

12. When installing the flywheel, clutch plate, and pressure plate, make sure you're installing them the right way around. To be fair, it is extremely difficult if not impossible to install them backwards or rotated the wrong way with the possible exception of the flywheel. As you remove your equipment, take careful note of which surfaces are facing outwards on each. There are index pins and certain orientations that will only allow for bolt holes to line up, but pay attention! The bolts you are re-inserting inside the clutch, as well as the ones securing the transmission to the engine, the driveshaft to the rear diff, midpipe to overpipe, and any hangars and cradles to the chassis, are the most important to torque to the correct specs. Use a torque wrench that you trust! Also also, be aware that some bolts the service manual states should be secured on the first few threads with e.g. threadlocker blue, or like on the flywheel need a small amount of grease on the threadside of the bolt head. Follow these instructions! The absolute last thing you want to have is a bolt coming loose in your transmission and turning into the worlds most expensive metallic gymnast. If you apply threadlocker where required, and torque your bolts to spec, you can sleep easy! The service manual does not instruct you to apply threadlocker to the pressure plate retainer bolts, however I did so because I've seen other videos of people disassembling their transmission and finding those bolts loose. It literally cannot hurt to do so. Just don't go overboard on applying threadlocker anywhere - only apply it to the first few threads of your bolts.

13. Re-mating the transmission to the engine is stressful: you're praying that all the work you're about to seal up at 37 ft-lbs of torque is mint, you're already exhausted from what you've accomplished so far, and you're trying to maneuver this 80 lb hunk of aluminum and steel into the back of your engine. I recommend taking a nice big deep breath before starting. This can either be extremely easy, or it can be a total PITA. The absolute best advice I can give is to play with the engine and transmission jack to try and get the mating surfaces of the two as flush as humanly possible. The index pins and key pins/holes have very literal tolerance for any difference in angle. Keep your eye on the width of the gap between the trans and engine. It should be uniformly wide along its entire circumference. An easy way to eyeball whether you're guiding everything in on center is to look at the bottom 2 index pins as they sit inside of the trans holes. It'll be very obvious if they're not centered in these holes, and you can adjust appropriately. The input shaft is tapered, so as you mate the trans to the engine, it will spin the handful of degrees to mate with the clutch plate. If you used your clutch alignment tool like you were supposed to, this should be a very smooth marriage of metal. Once you've gotten the transmission as far along the index pins and therefore as close to the engine as you can by sheer strength alone, you can start using the nuts and bolts to start working it the rest of the way on. You are going to want to do this slowly and carefully, alternating which bolt/nut you're tightening in a star pattern so that you are uniformly mating the trans to the engine. If you just try and tighten one at a time all the way down, you are going to torque the whole thing which will pinch the index pins/ bolts which will lock the trans in place until you back out and try again or do something as just flooringly stupid as try and force it on leading to stripped bolts and a brand new very expensive driveway decoration.

14. As you reassemble your vehicle, be aware of the "keyed" aspects of several parts. For example, the driveshaft connection to the rear diff. There will be marks on both the diff and the shaft indicating which holes line up. Why this is important, since all of the holes seem the same to me, I do not know however I believe firmly that if it wasn't important they wouldn't have bothered to decree it. Also, as you were mucking about with the shifter linkage, it is extremely likely you put the transmission into gear, which would make rotating the driveshaft to reconnect its bolts particularly impossible by hand. Do not freak out and think you've somehow screwed up the clutch install when the driveshaft doesn't spin when you definitely had it in neutral when you started this whole escapade. Just go back to the linkage and move the shifter into neutral from below the car.

15. If you replaced your release bearing and/or retainer cover, your clutch pedal WILL feel much softer, requiring much less force to actuate. Mine was so soft I actually thought I had screwed the pooch somewhere! But the fact is that you just removed a crusty, old, heat-cycled bearing and retainer cover with dead grease and replaced them with new, sparkly, smooth, and well-lubricated parts. This means you are fighting against much less friction to actuate the release bearing along the retainer cover collar around the input shaft. If it bugs you too much, there are many modifications dealing with springs and clutch fluid etc. that I won't go into.

There's honestly probably a whole book I could write on what I learned to do and even more so on what not to do.

I have never done an automotive job like this before in my life, and did it completely by reading this website and watching youtube videos, with the occasional reference to the service manual. Admittedly, I did have access to a car lift which made this project an order of magnitude easier. However, it certainly is not necessary.