FK8 Transmission: FIXING the GRIND

FK8 Transmission: FIXING the GRIND

If you have a FK8 or are thinking about getting one, then you’ll know that one of the biggest issues/complaints out there besides overheating, is the lack luster transmission that comes equipped on the car. First, one of the most noted and talked about problems is the 2nd gear grind, followed up quickly with the gear “lock out” issue. These issues have been documented not only on FK8’s that are driven hard, but also ones that have just driven off the lot.

Before I had even taken ownership of my FK8 I knew that the transmission issues were very real, and I wanted to take as many steps as I could to help reduce or fix these issues right from the start.  Below I will discuss and talk you through my steps I took to help remedy the issue’s.

Below I want to run through everything I think is necessary to help eliminate the dreaded grinding and lockout issues that plague the FK8 chassis. Along the way, I will also be go through the install process and procedure for all modifications discussed below.

Starting off, the first most important thing that was mentioned many times over was the clutch delay valve delete. Now, this isn’t a new tip or trick, plenty of other auto makers also equip their cars with a clutch delay valve. BMW, Ford, Nissan, Toyota, and pretty much all newer manual cars are equipped with some sort of CDV (clutch delay valve).

What is a CDV?

“A clutch delay valve is an automotive component added to the clutch system of an automobile to standardize clutch engagement speed. Its purpose is to engage the drive train of an automobile without introducing shock to the drive train components by engaging too quickly. By preventing drive train shock, CDVs also prevent an automobile’s balance from being upset, which aids in handling characteristics.

Clutch delay valves operate on the principle that engagement only needs to occur at a certain rate to be efficient and that engaging at a quicker rate can damage the drive train components of an automobile. Engaging the drive train to the engine too quickly can damage drivetrain parts, including the transmission, differential half shafts, axles, and CV joints.

Engaging the drive train too slowly can damage the clutch friction disc and cause clutch slippage.

Clutch delay valves operate as one-way restrictor valves that limit the volume of fluid that can move through the lines in a given time. This ensures a steady quick and firm engagement without being too fast for the drive train to handle since clutches can quickly disengage but re-engagement is damped. The clutch delay valve slows clutch engagement and was intended to reduce drivetrain shock in the event that an inexperienced driver quickly engaged the clutch at higher revs.”

Basically, that means that the delay valve will slow the movement of fluid that actuates the slave rod. The slave rod moves the clutch fork, and the clutch fork is responsible for disengaging and engaging the clutch. If the movement of fluid from the time you press the clutch pedal to the slave rod is shortened even by tenths or thousandths of seconds this can cause you to grind gears if you are shifting quickly or aggressively. Essentially you will be moving the shift lever before the clutch has disengaged completely.

Yes, this is a Civic Type R, the very pinnacle of Honda’s performance cars. It was designed to be raced, and it should have adequate components installed from the factory that will allow you the “race” the car. Well, sort of, there are some positives to a CDV as you just read. With inexperienced drivers this can save your driveline components, increase the longevity of them and even save you from a crash caused by disrupting the balance of the car by having the clutch engage to harshly. This can cause driveline shock and can jolt the car into unwanted positions while going through a turn.

With that being said though, this mod has had great results in helping people combat their grind issues across multiple automotive platforms. You shouldn’t be worried that deleting the CDV will greatly reduce the life of your driveline, because let’s be honest. 90% of the time you are driving the car like a choir boy and are therefore, shifting slow and smoothly. If you are driving around this way without a CDV there will be now increased wear on any driveline parts and the car will drive just as it did the day you drove it off the showroom floor. The only thing that needs to be noted is that you will have to make sure you have decent heel toe skills if you plan on taking your car to the track or going on spirited mounting drives. Once the CDV is deleted it will be sudden or harsh if you’re the type of driver that just puts the car in gear to down shift and lets out the clutch without revving to match engine speed. Most of the time the FK8’s auto rev matching will suffice. So, if you don’t plan of driving your car 10/10 on a track, you’ll be fine if you’re not good at heel toe. But this mod is plenty safe if you plan on tracking and are a smooth driver.

Keep in mind that I’m over exaggerating the effects that the CDV delete will have just to thoroughly break down how it works and to help teach others what exactly a CDV is. In my personal opinion, I bet you would never even really notice the CDV delete if no one told you it was done. You would just subconsciously adjust your driving style, just like you do when you drive a car that is not familiar to you. Except now you, will have the added bonus of no longer having grinding issues.

This modification is perfectly safe and many, many people have done CDV deletes across multiple platforms all with raving results.

When you delete the CDV there is no real noticeable difference in NVH (noise vibration harshness) and the pedal feel is the same as when the CDV was in. It is only noticeable when you are letting out the clutch to start off from a stop, it does engage slightly quicker and will require some getting used to but is in no way hard to get used to. Before long it will just become natural, and you’ll never even notice.

Now that you are more familiar with the CDV and what it does, let’s dive into deleting it. On the FK8 chassis the CDV is in the slave cylinder.

Start off by removing the air box, and coupler that connects the inlet pipe to the air box. You can also remove the cold side intercooler hose and tuck it out of the way if you need to have more access. The reason for this is you will need to disconnect the slave from the clutch line so you can get the slave completely out of the car and on to a work bench or table.

It is difficult to get the clutch line disconnected form the slave, so I ended up just removing the rubber clutch line from the hardline that comes off the chassis. Make sure to cap the hardline with some sort of rubber vacuum nipple or wrap it in a towel so the fluid doesn’t leak everywhere. Clutch fluid is brake fluid (if you didn’t know) and in this chassis the clutch and brake fluid is shared in one reservoir. This means if the fluid leaks all out you will have to bleed all your brakes too. Just don’t let all the fluid leak out and you’ll be good. If you leave the cap on the reservoir this will slow the leak of fluid and you should have about 20 min before the reservoir gets dangerously low and you need to re fill it. Remember though, as soon as you take the cap off the reservoir it will release the vacuum holding the fluid in.

Once you have removed the slave, it should look like the picture below. Make sure when you begin to try pry off the retaining clip you have the slave either in a bench vise or clamped firmly down to a tabletop. Removing the retaining clip is tough and you will need both hands.

See below where i’m pointing. This is where the small retaining clip is located.

You will need a very sturdy pick set. A harbor freight one won’t do here, you will just snap the tips off them. You will also need to use two picks it will not be possible with one pick.

Below you can see what it looks like all apart. The goal you are trying to achieve is removing the retaining clip (the thin C metal piece) this will allow you to get the aluminum slave seal out (small silver piece with the rubber O ring) and lastly take a straight pick and push through from the opposite side (the black hex nut where the clutch line was attached) carefully and slowly push straight through and the CDV (white plastic piece) will come out on the side you just removed the retaining clip and seal from.

Removing the retaining clip is VERY frustrating. Don’t get too angry, just take it slow and eventually you will get it to pop off. I mean it, I was just about ready to give up and put the car back together. However, it’s not impossible, it’s just a challenge and it is ok if you mare of scratch the top of the seal cap (as long as you don’t scratch below the rubber O ring.) If all else fails and you break your slave trying to do this, you can always just order another brand-new OEM one. Here is the part number 46930-TV8-G01. It might also be a good idea to buy a new one and try to delete the valve from the new one while it is already out of the car. Then, if you’re successful you can just simply swap slave cylinders and you wont risk having excessive down time on your car.

Once the retaining clip is removed you will need to take some thin needle nose plies and carefully grip the smaller top of the aluminum seal and work it out. You will need to use smaller needle nose pliers so they will fit and grip tightly on the cap. Once you are confident you have a good tight grip on it, work back and forth, twist and pull to completely remove the aluminum seal.

Only once the aluminum seal is removed is when you can take the straight pick and insert it on the opposite side and carefully push the CDV out.

Now that the CDV is out, you can now simply reinstall the aluminum seal making sure the smaller nipple part is facing outward. Then once fully seated you can reinstall the retaining C clip. Now you can reinstall the slave cylinder in the car. (pro tip* Use some lube on the small rubber O ring so it doesn’t get pinched or torn as you slide it back into the slave. The tolerances are very tight!)

Deleting the CDV means you are simply removing the white plastic piece. There is a spring and ball in the CDV that all stays in the white plastic piece, you don’t need any of that. I want to make it as clear as possible, just simply pop out the white plastic piece and throw it away. Reinstall the aluminum seal and c clip and go. It’s really that simple. The hardest part is removing the retaining clip.

Since I knew getting to the slave and deleting the CDV was going to be a challenge. I figured while I was there, I would also replace the stock rubber clutch hose with a SS braided one. This will increase the pedal feel slightly, but not much more from the stock feel. Installing a SS clutch line will allow the fluid to have just a bit more pressure in the clutch system. This in turn will increase the response time of the fluid movement to the slave when the clutch pedal is pressed.

We are only talking about a few microseconds here, but it all adds up to help ensure you don’t have any grinding issues. Note: This alone will not fix your grind issues. Most people that do the CDV just keep their stock rubber hose and still can get rid of the grinding issue. This is only and extra measure that I took to help ensure the clutch system is working as well as it can. You don’t have to get a spoon clutch line, there are a few other companies that make SS lines that cost 60-75 bucks compared to the spoon 120 bucks. Any SS line will be an improvement and honestly spoon is overpriced but I had to buy it to stay true to my JDM roots.

This install is self-explanatory, especially if you have removed the slave with the rubber line attach to it still, like I did. Simply unscrew the stock rubber hose from the hardline coming off the slave, then attach the new SS line and then when you reinstall the slave, simply connect the SS line to the hardline from the chassis.

You can see a couple installed pictures below.

In the picture below you can see how I disconnected the rubber intercooler hose from the aluminum intercooler pipe that goes across the transmission. I left the rubber intercooler hose connected to the intercooler and just tucked it out of the way to gain easier access to all the clutch line stuff.

Once you have the salve back in and the lines all re connected, it’s time to bleed the system. This is done just as you would any other clutch. Have someone in the car pumping the clutch pedal, then have someone else opening and closing the bleeder valve on the slave. Person in the car: pump the pedal 1, 2, 3 times and hold. Person outside: crack the bleeder allowing the pedal to travel all the way to the floor, close the bleeder. Person inside: most likely the pedal with be stuck to the floor, this is ok, simply lift it and do the sequence again. Pump 1, 2, 3 times and hold while person outside opens and closes valve. Repeat this sequence about 5 times or until there is no more air bubbles coming out with the fluid. (Pro tip* use some sort of rubber hose or silicone tube to slide on the bleeder valve so when you open the valve the fluid doesn’t go everywhere. Most people will just run the tube into an empty water bottle to collect the fluid.)

Last part of clutch delay valve delete (arguably one of the most important ones for the FK8) is to adjust the clutch pedal throw. Adjusting the pedal throw will essentially change where the clutch engagement point is along the pedal stroke. For some reason, on the FK8, from the factory the clutch engagement is set pretty “low,” this means that you barely lift the clutch pedal from the floor to start engaging the clutch (make the car start to move) While this is the preferred feel for most people, it’s not always the best thing for the car. With a low engagement, that means that you must push the clutch pedal a lot further down to disengage the clutch when shifting gears. Remember we are talking about milliseconds here, but with the FK8’s issues, every little bit will help.

Keep in mind that it is possible to adjust it too much one way and too much the other, so make sure you are making small adjustments. Basically, what we are trying to do is eliminate the “slop” or “play” in the clutch pedal. As it comes from the factory there is a lot of slop in the pedal, which basically means that there is movement towards the floor without actually putting pressure on the clutch master cylinder. Below is how you are going to be adjusting the slop, which will in turn allow you clutch to disengage sooner when pressing the pedal (basically moving the fluid sooner in the clutch line, which will then make the slave cylinder rod move sooner, which activates the clutch fork, when disengages the clutch so you can shift gears.) WOW, I know that’s a lot to take in and that I’m really overstating the obvious, but I’m just trying to make it super clear as to why this is necessary.

This is easily done by looking under the dash where the clutch pedal is. You will identify the master cylinder rod that connects to the clutch pedal. (See below) You are going to need a 12mm wrench:

· Step 1. Take the 12mm wrench and put it on the jam nut on the rod.

· Step 2. You are going to rotate the wrench clockwise (as if you are sitting in the driver seat looking forward) This will also most likely be pulling down on the nut. This is going to loosen the nut

· Step 3. Once the nut is loosened, you are now going to twist the rod with your fingers in a clockwise rotation.

· Step 4. As you are twisting clockwise, move the clutch pedal with your other hand back and forth until you feel the slop is gone.

· Step 5. Once the slop is gone retighten the jam nut.

It is important that you DO NOT adjust it too far. If you adjust too far and there is tension, the clutch could potentially never fully engage, and this will cause you to overheat your clutch. Don’t be scared though, you would really have to twist the rod very hard to get to that point. Just turn the rod with your two fingers, it should be very easy to turn and when it gets slightly hard to turn, stop and tighten the jam nut. (Also please don’t mind the horrible pictures below, it’s very hard to take pictures under there. They are only used for demonstration purposes only. (ha-ha)

Pictures below shows what the clutch rod looks like and you can see the 12mm nut on the left side of the rod

Last part to adjusting the clutch rod is to identify the 17mm bolt and jam nut that are the pedal stop. You will now need to slightly increase the amount of up travel the pedal has. This will ensure that your clutch will completely engage and that you will not over heat the clutch after adjusting the clutch rod.

You are simply going to loosen the 17mm jam nut, then turn the bolt 1 full counter clockwise rotation, then re tighten the jam nut and you are all done.

Next thing I did to help fight the gear grind issue and improve shifting feel was install some Acuity shifter bushings.

Again, start off by removing the air box. You will also need to remove the battery, battery tray, and the aluminum intercooler pipe that goes over the trans. These are all very easy to remove just unbolting a few bolts, some hose clamps, wiring clips, and removing a rubber hose.

Below in the picture you will see I am pointing to the stock shifter bushings that we are going to be removing. You can also see the battery tray in the upper right of the picture and how it’s in the way of getting the charge pipe off. When removing the battery tray, pay attention to the bolts being removed. Some are longer and some are shorter and go in specific holes when reassembled.

Below you can see what I have had to remove/disconnect to be able to remove the alluminum intercooler charge pipe.

Below you can see what it looks like with the aluminum charge pipe removed. You can also now clearly see the two bushings that we are replacing.

Seen below are the spring clips that hold the shifter cables to the bracket on the transmission. These must be removed to allow enough movement in the cables to remove the stock bushings.

Below you can see what it looks like with one of the stock bushings removed. To do this just simply place a thinner type of screwdriver directly into the hold of the bushing and carefully pry out.

Once you have removed both OEM bushings, simply install the new Acuity ones and reinstall the cables in reverse order of how you took them apart. This is a super easy install, but is just time consuming because of the amount of stuff you have to remove to gain access to the bushings.

Now reinstall the charge pipe and ensure that you have tightened all hose clamps securely. If not, you could get boost leaks or worse yet have your intercooler lines pop off. You can now also reinstall the air box, battery tray, and battery. Keep in mind, since you have disconnected the battery there will be a Christmas tree of lights on your dash when you go to start the car. Don’t freak out, this is ok. Just drive the car normally for about 10-15 minutes and the lights should start to go away. If they haven’t all gone completely, you can turn the car completely off, wait 30 seconds, then restart the car and continue to drive. This should clear the lights completely. All the sensors just need some driving miles to relearn since you have removed the battery and cleared their “memory.”

Last part to the list of upgrades that all combined help to ensure no grinds or lock outs is, RMM (rear motor mount)

If you frequent my blog, you’ll know that I installed these on both my 2009 Civic and Angie’s 2019 Fit. In both cars they made a huge improvement on shifting, and braking. (If you want to read more specifically about my RMM experiences on my FA1 chassis, click the link below to go to my other post I have about installing it on my 2009 civic)

Installing a RMM on the FK8 chassis is stupid easy. Hardest part is probably jacking up the car and getting it on jack stands.

Once jacked up you are going to simply remove the aluminum under tray, unbolt the two bolts that hold the stock mount on, slide the OEM mount out, slide in the new mount, then reinstall the two bolts, the aluminum under tray and then lower the car back on the ground. This is such an easy modification! Anyone should be able to do this regardless of your mechanical skill. (Pro tip* be sure to lube the bushings on the mount slightly so they slide in much easier.)

Below you can see what it looks like installed. Keep in mind that if you have a stock front pipe then the motor mount installs very easy. If you have an aftermarket front pipe you are most likely going to have to remove the aftermarket front pipe to allow for the bolt to come out to remove the motor mount. This is because usually aftermarket front pipes are 3inch diameter so there is not enough room to slide the bolt out.

On my other two cars that installed the Hasport RMM I got the u62a bushings and noticed only slight increase of NVH. So, for the Type R I figured I would also order the u62a bushing and… I hardly noticed any NVH at all and to be honest, I didn’t notice as much of a performance improvement as I did on the other two cars that I had previously installed the same mount on. I’m pretty sure I’m going to upgrade to either the Hasport u70a one, the 27won mount, or most likely I’ll just get the Hasport u62a two side mounts to have a complete mount upgrade. With the 27won, it’s no secret that there is a noticeable amount of NVH, but I feel like that will yield a better performance increase compared to what I currently have installed. With the Hasport u62a one I currently have installed; the wheel hop is substantially less, and the shifting did improve. However, there is still ever so slightly some small amount of wheel hop, and I was hoping to eliminate it completely. I would say get the u62a Hasport RMM if you are Nazi about NVH, because there will quite literally be no difference in NVH compared to the stock RMM and you will still have some performance increase too. If you are more of a serious enthusiast, I would suggest getting the Hasport u70a, or 27won mount. If you’re like me and you bought the car exclusively to track and it’s not your daily, I would go with the full Hasport U62a mount kit (all three mounts)

While I cannot confirm nor deny if these will completely eliminate any possibility for grinds for everyone. These are the steps I took to help ensure that I never have a problem with grinding or locking out. I was so concerned about prematurely damaging my transmission, that I quite literally installed all the modifications before I even had 200 miles on the odometer. I never had a grind for the first 200 miles, but I did drive it incredibly conservative. After installing these modifications and making it past the break in period I was finally able to beat on the car heavily. Now having 2,500 miles on the odometer I can still say, hand on heart, that I have not had one single even slight hint of a grind or lock out. I have not yet changed the trans fluid, it is still the OEM Honda fluid that came with the car. Yes, there are people that say switching to “Amsoil”, or “AC Delco synchromesh friction modified PN# 10-4014” can also help fix the trans grind issue without even having to do any of the modifications I mentioned above. For me, I felt like the fluid is nearly a band aid and doesn’t help solve the mechanical issues of the transmission. While the fluid does aid in allowing the gears and synchro’s to slide together more easily, there could still be increased wear or slight grinding that is happening and you may not know it.

That being said, I will eventually change out to one of the popular options of trans fluid for this car. When I do though, it will only be even more of an improvement on the transmission since I have already done the other supporting modifications too.

If you only want to do one of these modifications, I would do the CDV, this is clearly a scientifically proven issue among multiple car manufactures and it clearly makes the most sense. If the fluid is slightly delayed, then the shift must therefore be slightly delayed (meaning you can’t shift quick). However, the 5 combined modifications mentioned above are relatively cheap. The CDV delete and clutch pedal throw adjustment are free. This leaves only three other things you would need to buy: SS clutch line, Acuity bushings, and RMM. This is a total of 300-400 bucks. In the grand scheme of things. This is hardly any cost at all to help ensure your car works properly and doesn’t have shortened transmission life due to grinds or premature ware.

For the people that are worried about NVH or drivability… Trust me, with the 5 modifications mentioned above my car still drives and feels just as it did when I drove it off the lot. Only thing that has changed is the fact that the transmission shifts sooooo much smoother and more direct into each gear. I would HIGHLY recommend doing all these modifications to your FK8!

Thank you for taking the time to read my blog, and I hope you were able to learn a few things. If you have any questions regarding this post or any other blog posts, please feel free to reach out to me. Email Billy@Functiontheory.com, Instagram @Functiontheory, or just simply comment below and I will get back to you. If you happen to live in or near Las Vegas and would like some help to do these modifications, I would love to come help you out.

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