DIY - Swap clutch slave cylinder for improved feel and control
 

The stock setup of the clutch is frustratingly vague because there is too much leverage between the clutch pedal and the pressure plate. I started looking for ways to change the diameter ratio between clutch and master cylinders when I stumbled into the no-brainer solution. The stock slave cylinder has a 13/16" bore. Subaru has another clutch slave cylinder with a slightly narrower bore of 3/4". It is otherwise identical to stock but decreases the leverage by 17%. Here is the original thread leading up to this DIY. Enjoy.

Update 07/27/15: Added links to parts from NAPA and Autozone

Update 05/13/15: ck-GT86 generously added his procedure to upgrade the hydraulic line in concert with this swap. Skip forward to his post here. The link is also repeated below. Thanks, @ck-GT86.

Update 12/15/14: Drain, plug, and save your original slave cylinder. It will come in handy if you ever boost enough to require a heavier clutch. Thanks, @Koa.

Update 12/11/14: Added table of manufacturer's torque specifications. Thanks, @JB86'd.

Update 11/26/14: Corrected references to socket size. 14 mm was 12 mm. Thanks, @Phantobe.

Update 11/14/14: On discussing with some fellow members, if you are already running an aftermarket clutch with a stiffer pressure plate this may not be the hot ticket. This mod increases pedal stiffness. It's comfortable on the stock pressure plate but might be too much for a big-boy clutch.


Precautions:

1. Brake fluid will eat paint. Be very careful to avoid spillage onto any finished surfaces. If any is spilled, stop working. Immediately wash and rinse all contaminated surfaces.
2. Brake fluid is toxic. Use nitrile gloves and/or wash hands immediately after contact. Dispose of used fluid and any contaminated items in accordance with local, state, and federal law.
3. Inspect your clothing. Zippers, buttons, rivets, etc. will scratch your car. Consider using a fender cover while working.
4. Cleanliness is key. The slightest particle of grit or schmutz will settle to the bottom of the cylinder and cause premature failure by grinding back and forth with each operation of the clutch.

Tools:

socket driver
14 mm socket
6 in extension
8 mm combination wrench
torque wrench (recommended and easily rented)
1/2"female-to-3/8"male adapter (if needed for torque wrench)

something to tie the loose end of the hydraulic line to the strut brace

a partner to operate the clutch pedal when bleeding the new cylinder

Consumables:

1 pint DOT-3 brake fluid
Shop towels or rag big enough to absorb 1-2 oz brake fluid.

Parts:

1 ea. Subaru 30620AA111 (or equiv.) slave cylinder

NAPA Altrom atm p3038 (Nabco just like OEM)
Autozone Duralast 900061

2 ea. Subaru 114130151 (or equiv.) gaskets (crush washers) for 10 mm banjo fitting

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Torque specifications:

http://www.ft86club.com/forums/pictu...pictureid=8688

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Preliminary steps:

1. If not already adjusted for minimum usable height, perform the Clutch Engagement Adjustment.
Although not required, be prepared to perform a second adjustment after installing the new cylinder. The smaller diameter of the new cylinder will slightly raise the touch point.

2. Inspect the new cylinder for any obvious defects. Do not remove the rubber stopper from the new cylinder. It will be transferred to the old cylinder just prior to removal.

3. To minimize the possibility of particulate contamination, before disassembly, thoroughly clean the hose, banjo fitting, AND the 14 mm socket.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Procedure:


To prevent fluid loss, be prepared to lift the loose end of the hose above the fluid level in the reservoir immediately after unscrewing the banjo bolt.

http://www.ft86club.com/forums/pictu...pictureid=8582




http://www.ft86club.com/forums/pictu...pictureid=8581

http://www.ft86club.com/forums/pictu...pictureid=8583


Now we're ready to disconnect the banjo fitting.

Place another towel within reach. Use the ratchet only to loosen the bolt. Use your fingers to unscrew the bolt most of the way.

With towel in free hand, prepare to cover the end of the banjo bolt and fitting.

Remember, there is a gasket (washer) both above and below the banjo fitting. Be aware of the lower one. It should stay with the cylinder.

Leaving the bolt inserted in the banjo fitting, immediately lift both up and away from the cylinder.

Observe how slowly the fluid oozes on its own. This knowledge will come in handy when reassembling the fitting.

Separate and set aside the bolt and old gasket.

Tie off the hose.

Inspect the area for, and remove any spilled fluid.


http://www.ft86club.com/forums/pictu...pictureid=8646

http://www.ft86club.com/forums/pictu...pictureid=8585


***Ignore the removal of the reservoir cap at this point. It is vented and therefore will allow the fluid level to equalize.***

http://www.ft86club.com/forums/pictu...pictureid=8587



Remove and set aside the remaining gasket.

http://www.ft86club.com/forums/pictu...pictureid=8586

http://www.ft86club.com/forums/pictu...pictureid=8592


Using a rag to prevent spillage, set the cap into the old cylinder.

Note for working without a torque wrench: The mount bolts will feel especially tight and may first come loose with a "snap." Do not use this as a gauge for torquing the bolt upon assembly. Try to feel for where it's good and snug but doesn't stretch the threads. It can help to get a feel for that sweet spot by repeatedly tightening and loosening the bolt each time increasing the torque a smidge. The fastener will settle in over time but if you're not sure, keep the ratchet in the car and check it the next time it's cold.

Remove the 2 mount bolts and remove the old cylinder.

http://www.ft86club.com/forums/pictu...pictureid=8593


Mount the new cylinder and if upgrading the clutch hydraulic line, follow ck-GT86's procedure here.

Quickly, using 2 new gaskets, mount the banjo fitting.

Tighten the banjo bolt only until snug. Then continue turning the bolt 1/2 turn to set the gaskets. [service manual specifies 13 lb-ft torque]

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Bleeding the system
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Note: The clutch pedal will not return on its own if the assist spring remains installed. This is normal.

Caution: Monitor the fluid level in the reservoir carefully. If the master cylinder is allowed to suck air, bench bleeding will be required to restore function.

1. Have your partner prepare to press and hold the clutch pedal.

2. Establish a clear method to communicate with your partner. This may seem odd but with the repetitive nature of this task, an "oops" moment is a very real risk. It's not a big deal, just a little frustrating when "Arrrgh!" You almost had it.

3. I bleed the clutch fluid into a rag because there's less risk of spillage and it's easier to feel presence of air that way.

Procedure is as follows:

1. Press clutch pedal.
2. Slowly open bleed valve. (listen/feel for air bubbles)
3. Close bleed valve.
4. Lift or release clutch pedal.
5. Check fluid in reservoir and add if required.

Repeat this cycle until all air is eliminated from the system. It will be easy to feel this. Yay! Enjoy the new sporty feel of your clutch.

https://www.youtube.com/watch?v=uLj-qA25EXM

1 ea. Subaru 30620AA111 (or equiv.) slave cylinder

Is this a larger or smaller diameter cylinder than our factory slave? For "feel and control" would that be a larger diameter cylinder which would take more pedal movement?

The factory BRZ/FRS slave is 13/16". The 30620AA111 is 3/4" and 1/16" smaller than stock (approximately 15%).

By shrinking the slave you reduce the amount of distance that the master needs to travel to create the same amount of motion. This allows pedal movement to be reduced. That reduction creates a more tactile range of motion during said pedal movement, returning the "feel" that many of us miss having in this clutch system.

Oh I cant wait for this :thumbup:

I hate the feel of the clutch in this car (even after I adjusted the position)

Finished. Go for it.

so is the crush washer just a standard 10mm? I am picking up my new slave today.

Yup. nothing special. I got mine off of the rack at a generic parts shop.

You the man, Ultra. Trying this during the weekend. Parts just came in :)

Thanks for the help earlier last week as well

Thanks for the DIY post. Interested in hearing from guys who have done the pedal adjustment, and removed the helper spring and how this compares.

My pleasure!



Can't tell you how excited I am for you all.

Well i just finished mine. I have a little bit of adjustment on the pedal still but man is it better. There is an engagement point now. It is so much less vague. Thanks for figuring this out. I wanted to add a few more part numbers for everyone.

I got my part from autozone
part # 90028
Subaru part # 30620-aa041

Still 3/4 and fit perfectly

Great now you get it posted! After the snow is on the ground. It will just have to wait till spring now I guess.

How much was it?

like 21$. it was a good deal

Can you provide a pic of the box? I'm pulling up nothing at Autozone's website parts catalog for #90028. Am I missing something?

hmm...I tried calling the one near me, and *shocker* the guy had no idea (and no, I didnt say what I was using it for-just tried to have him look up the number.) The 90028 pulled up nothing, and the oem # just came up at almost $100.

Trying another one haha

Yeah, I got nothing too.

I think that part number might be wrong, the OEM part number WE WANT FOR UPGRADE is 30620aa111

So, I called autozone again, and gave the proper OEM# (30620aa111-which is the 3/4 one) and they pulled it up as $23.99

autozone Part # 52337 or alternate # LSC337

Okay, here is the AUTOZONE BREAKDOWN:

The correct part to order is "900061"-CLICK for Link Which is $31.99 (11/18/14)

Part #52337/alternate #LSC337 will fit. However, the mounting point for the clutch line is oriented differently, so this is not ideal.

I grabbed the linked one below. Not installed yet.

http://www.autozone.com/drivetrain/c...er/383444_0_0/

Edit: So if you look @ vehicle fitment on both links... The one I posted is for 2007 & newer the other one posted is for 2005 & older. I wonder what the differences are...

haha. When I called the first time, the guy came up with that part number/price. I guess we'll see lol

I think it could be wrong...

http://parts.subaru.com/p/Subaru_200...0620AA042.html

Take a look, different PN & matches with vehicle fitment on Autozone. I'll take a closer look when I'm home...

That's the wrong one, just like the one I installed but didn't feel like exchanging. It works just fine if you mount the banjo fitting outside of the guide in the casting. Not optimal because it "might" vibrate loose. I've been watching mine. No way is it going anywhere.


Get the right one. @Phantobe has it. Autozone P/N 900061

The rough casting is different. The older one is actually a little shorter (no problem for us) and the guide for the banjo fitting is perpendicular to the centerline of the cylinder.

Yours, the correct one, has a guide oriented at 45° to the cylinder.

Sweeeeeet...

Are the washers also referred to as "brake line washers"?

http://www.autozone.com/brake-system...er/773866_0_0/

Was gonna grab those instead of OEM.

Yup, 10 mm is what you want.

Sorry guys. it came in a bag with the 90028 number on it. Let me see if I can still find the bag today. Its a duralast part if that helps. When I went I gave them the oem 3062aa111 and that is what they gave me.

if you gave them the 3062aa111 number, they probably gave you the "wrong" slave. IE, the fitting on it faces a slightly different way. Still fits though, but the line could have extra stress on it since it points the banjo fitting further away.

I installed mine last night, everything went on just fine. Since I'm running the "wrong" one, I might remove the bracket between the hardline and the rubber line and bend the metal hardline so its a little closer to the slave. Or just replace the whole line entirely with an aftermarket one.

You could install the banjo like the photo I posted here in @Ultramaroon's original thread. It's not ideal but would work to keep the banjo from loosening the bolt. I believe @Ultramaroon is currently using this as a workaround with his slave.

You are correct, sir. It's holding up perfectly but I'm feeling a little guilty about half-assing the photos. I'll replace the replacement with the correct one and update the photos in the OP soon.

Edit: I haven't replaced it. Works fine. I'll get the correct one when this one is no longer serviceable.

I did @37's solution. It's not going anywhere. Recommend doing that so you're not tweaking the hose. No need to bend anything.

Originally when he and I were discussing braided or otherwise stiffer lines, I kinda thumbed my nose at the idea thinking "great for brakes, meh for the clutch." I've come around a bit. It certainly can't hurt. :D

Just did this today clutch feels much better, can confirm that the slave cylinder I purchased fits great (from autozone).

Followed the DIY with caution, everything turned out good.

Shifting is much more fluid, downshifts & upshifts are smoother! Thanks @Ultramaroon , learned a thing or two :D

Congrats, man! Just in time for the Thanksgiving road trip!

Would you add or change anything in the instructions? Anything I could clarify?

Let's see...

Well I didn't really need to use a bungie cord to hold the hose, I just routed it so it wouldn't move & was sitting vertically.

For whatever reason the two bolts mounting the slave to the bracket...those were a friggin bitch to get off, I used a 3/8 drive & I could have used more leverage.

I would add approximately how many pumps it took to bleed the cylinder, only took me like 3-5.

how much stiffer you reckon it became? slightly worried as I have already removed my clutch spring. Also is there now a definitive touch point that can be felt through the pedal?

Thanks in advance

A good amount stiffer. If you have this mod plus the spring removed it's gonna feel very stiff.

The touch point is more definitive than the squishy feeling oem clutch.

Finally feels like a proper clutch after doing this. After a year and a half I can finally forget about the clutch and driving smooth in traffic is now easy. I adjusted the pedal level with the brake pedal and reinstalled the return spring.

I've done the return spring removal and pedal adjustment slightly above the brake pedal, and although it's soo much better now, I've gotten used to it and the clutch feels mushy again. I'm considering doing this but I've never bled a clutch or brakes before, and I'm a little apprehensive about messing something up. Are there any potential problems the change in diameter/stiffness could cause to the clutch system?

Clutch pedal rebound force increases by only 17%. This is a marginal decrease in leverage but is just enough to restore that "feel."

There are no inherent problems with this change. The only possible issues would result from errors in performing the procedure.

1. Contamination of the hydraulic system. Cleanliness is key.

2. Air in the system from incomplete bleeding or by draining the reservoir. Follow the procedure carefully.

I did this operation a few weeks ago, and wanted to hold off before giving my report. The install itself was simple and Ultra's details, including the rag around the hose etc are important!

Clutch & tranny Set-up:

- Stock clutch & flywheel
- Clutch engagement screw adjusted, pedal slightly lower than brake pedal (I know, such empirical and accurate measurement)
- Motul 300 tranny fluid (not the best cold, but once warmed up is predictable and smooth- well documented so I won't go much into it)
- Return spring in
- Whiteline Transmission insert
- Perrin rear shifter bushing
- Mtec springs

I added this clutch slave cylinder after the aforementioned mods. Overall, it ties the whole package together imo. The clutch pedal adjustment attempted to set the overall clutch characteristics more akin to what many of us are used to; the whiteline tranny insert (as well as diff+subframe bushing kit) tightened up the drivetrain; the mtec springs and Perrin rear shifter bushing helped with providing more positive and engaged shifts. But this mod has been one of the best $50 I could have spent on the whole driveline experience. Clutch pedal is springy, yet not taxing. Even in heavy stop-and-go (I'm talking about Seattle bridge at rush hour stop and go), the engagement point makes itself known each and every time, with crisp biting points and little vague-ness about it all.

I used the OEM subaru slave cylinder detailed in earlier posts and some crush washers. I commute 100 miles a day and have really enjoyed being able to listen to music and still find the engagement point as easy as in my old WRX.

10/10 old chap!

So, how is it?

Edit: I see#38 now.

His post about his reaction to the mod is literally the one right above yours, haha

Just bought the parts for this yesterday, but my car is off the road for the winter so I won't know the feeling until next Spring.

Thanks for the write-up @Ultramaroon