By on December 17, 2015


clutch. Image: Shutterstock user Somchai_Stock

James writes:

Hi Sajeev,

I’ve got a 2003 Impreza WRX (blob-eye) that’s covered 96,000 km now. I bought it two years ago from the original owner, who seemed to take very good care of the car (every receipt since new). The car has been almost faultless.

About 4,000 km ago, at 92,000 km, the original clutch was clearly on its last legs. Under wide open throttle in 3rd gear, the clutch would slip and struggle to get power down. So off it went to a local WRX specialist to have the clutch replaced with a new kit: new pressure plate, machined flywheel and new Exedy OEM (standard, not heavy duty) replacement clutch.

However, when I got the car back, it felt completely wrong.

With the OEM clutch, you could roll and creep around the place smoothly when you took off using just the clutch. This new clutch makes a terrible shudder, and the front end vibrates pretty bad. The car does take off smoothly with throttle applied, but it won’t be very smooth if you catch the clutch in a bad mood. The clutch also has a bad habit of shuddering on downshifts, especially at lower revs.

My mechanic told me to give the clutch time to “bed in” and said it’d get better. After 1,600 km, with little to no improvement, they admitted the clutch might be a faulty unit, and replaced a new clutch kit free of charge.

Since then, the clutch has felt better than the first replacement — but not by much after 1,700 km. I went back to my mechanic and, while they said “it wasn’t perfect”, they wanted me to bring it back in another 1,000 km to see if it hadn’t improved. However, it just seems weird that the second clutch is still displaying the same problems. What could be the issue here? Bad flywheel? Improper installation? Another faulty clutch?

Sajeev answers:

I was concerned the Exedy WRX clutch might have the same issue as my go-to aftermarket clutch: the “King Cobra” for small block Ford products. The unit in my brother’s Fox Mustang (light, by cable-operated standards) is very different than the newer one in my Fox Cougar (much heavier). Not enough to bother me, but I digress.

Exedy says their Pro-Kit clutch is “manufactured on the same production line as OEM clutch components.” The Internet also agrees. And the Internet is NEVAR WRONG!

That means one of your final questions might contain the answer, but swap “flywheel” for “pressure plate with a bad spring.” Or maybe the rod between the pedal and hydraulic cylinder is out of whack. And yes, perhaps there’s a batch of bad clutches from the factory! I’d read this thread first, then discuss the condition of the pressure plate and, lastly, consider blaming it on a bad batch of clutches.

Bonus! A Piston Slap Nugget of Wisdom: 

It’s theoretically possible — but not probable — that a leaky rear main seal could contaminate the clutch. It could cause clutch chatter if oil reaches the friction material. Considering its improbability, plus the seemingly well maintained, stock (?), unabused nature of your WRX, this doesn’t seem likely. 

[Image: Shutterstock user Somchai_Stock]

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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42 Comments on “Piston Slap: An Exedy-ous from Logical Clutching?...”

  • avatar

    Sounds exactly like the clutch on my 99 wrangler. It was replaced about 40000 ago and has always acted that way.

  • avatar

    How bad is it? Are you sure it’s the clutch?

    My car has a hideous shudder, but it’s NOT the clutch. It’s an ’03 protege with blown engine mounts. I replaced the front one and it helped. A ton. But the problems still exists because the back mount is entirely delaminated.

    Maybe you’re smarter than I am, but I thought my problem was clutch and it totally wasn’t. So make sure you keep an open mind.

  • avatar
    bumpy ii

    Check the hydraulic bits, make sure they’re not leaking. Make sure they didn’t reuse the throwout bearing. If there’s any adjustment on the clutch fork, check that.

    However, I think the new cluch is simply more aggressive than the worn OEM clutch you were used to. If you do want that easy touch, you might have to put in an actual Subaru unit, rather than whatever Exedy thinks “OEM” feels like.

    • 0 avatar

      Could be. I’d have to drive it to tell. If there is a problem, it’s hard to name it without seeing a picture of the flywheel and clutch kit disassembled. Have your guy try a different supplier next time.

  • avatar

    It probably won’t help the poster much, but there were many complaints about clutch shudder in early WRXs.

    My brother’s 2002 WRX had three free Subaru Canada replacement clutches, none of which cured the problem, so he traded it in on a Passat W8 6MT, where with his usual luck he got 6 completely trouble free years of below the radar enjoyment.

  • avatar

    A well maintained vehicle having its clutch go out at less than 60,000 miles? Either the original owner abused it or just didn’t know how to drive a manual. Receipts or not I would be very concerned aboot the rest of the car, guy.

    • 0 avatar
      heavy handle

      The WRX is 4WD, meaning that you get a lot less tire slip. That slip has to go somewhere.

      • 0 avatar

        Clutches wear when they are partially engaged. The vehicle being AWD has nothing to do with that. Clutch wear is determined by how much torque is transmitted through the clutch while it is partially engaged. Also, the rate of wear increases greatly at elevated temperatures, so repeated slipping will destroy a clutch in a short period of time.

        • 0 avatar
          heavy handle

          To put things a different way: because the WRX is 4WD (and high performance), drivers spend more time with the clutch partially engaged and slipping.

          2WD vehicles get wheel slip under the same circumstances, and most AWD cars and SUVs are actually 2WD until the center diff engages.

          Something’s got to give. Typically with Subaru, it’s the clutch.
          Others have speculated that WRX clutches are deliberately weak to protect much more expensive drivetrain components. It would certainly make sense.

          • 0 avatar

            That point is valid only during aggressive driving with frequent hard launches. Something that’s very likely considering the car is a WRX. it’s not a car usually purchased for church runs.

          • 0 avatar

            Whenever I try to brag that my clutches have lasted 120-140k (miles, that is), someone chimes in with clutch that lasted 2x that. As far as hard launches, a friend had an Evo 8 making 340 whp that he occasionally dragged and auto-crossed and it made it to 87k. Anecdotes are not data, but I would be worried aboot the car, friend.

          • 0 avatar

            It’s only weak if you boost up the motor without realizing you need a new clutch and stronger gears, too. It’s worth it to get some better ratios while you’re at it. Stock I guess you can do some damage if you’re absolutely terrible, but most broken bits are the result of extra power.

            My 05 WRX is at 156,000 miles on the original clutch. But since I live close to work and can bike or take the train it’s all from road trips. For all I know it’s metal on metal by now and I’m just that used to it. Exedy makes the original clutch, too, if I recall.

    • 0 avatar

      Some people just slip the clutch a lot. Often it’s the most conservative drivers that do so. I don’t consider that abusive to anything but the clutch.

      On the other hand, it may have seen a lot of side-step launches!

  • avatar

    Was the pressure plate replaced and the flywheel resurfaced when the clutch was replaced? That’s what I did when I replaced the clutch in one of my cars and it’s smooth as butter. Good luck.

  • avatar

    I’m going to have to agree with Detroit-Iron here. Barely 60,000 miles on a clutch is not normal. You’d need a lot of aggressive clutch slipping launches to do that. Worn engine/transmission mounts from aggressive launches could definitely cause that a shuddering. Might be something to look into.

    However, a quick browse on the Subaru forums seems to suggest you have two problems:

    1. You had the flywheel machined. Subaru recommends replacement, not resurfacing.

    2. Everyone seems to complain about Exedy clutches chattering in Subarus.

    • 0 avatar

      Unless it’s 60k HARD city miles, I agree. 165k miles and still going strong on our “junk” (as most refer to it) OEM VAG clutch. Super smooth shifts and still holds perfect under WOT in every gear.

      • 0 avatar

        I did 130,000 miles on a Mk I Focus, 85% city miles, and the clutch was still perfect when I sold it. I’ve never had to replace a clutch in a street car that I’ve driven.

        I worked for a Mazda store back in the 80’s, probably half the vehicles we sold had manual transmissions. We only rarely did a clutch job and didn’t sell many clutches over the counter.

  • avatar

    There are a few things at play here but I will share some of my experience with various Subaru clutches.

    First, 96,000km seems like too soon for an OEM clutch to start slipping. I have seen many get to 150,000km or more easily so there might have been some learning and/or abuse on this clutch.

    Resurfacing the flywheel is fine in most circumstances but I have seen some resurfaced flywheels that cause chattering issues.

    Sajeev’s statement about the rear main seal is spot on. Any oil or grease on the clutch disc will cause chattering issues.

    You did not mention the throwout bearing but I am assuming it was replaced since it comes in most kits. If not, that could be part of the issue.

    There have been issues with some of the Exedy throwout bearings in the past so even if it was replaced it might be part of a bad batch.

    I have seen chattering in some brand new clutches last for a couple hundred miles and then go away so yours might just need to be broken in.

    The clutch fork has been known to bend or break when abused. It is a $20 part so I usually replace it when replacing clutches on these.

    My recommendation right now is to drive for a while and see if the chatter goes away as it breaks in.

  • avatar

    I go with previous comments: Likely problem is the flywheel and or engine/trans mounts. The WRX with its HiPer rep is almost asking for clutch abuse. The clutch should be used like a switch to change gears and start off from a stop. If someone has got their foot on the pedal most of the time, slipping it like they are on an MX bike, clutch life will be short. Also flywheel will usually be overheated and warped and require replacement. I’m not that familiar with the WRX clutch/flywheel, but many flywheels cannot be successfully resurfaced.
    Some repair shops advertise low-ball prices on clutch replacement without including any flywheel work/replacement. Sometimes you can get that to work, sometime you don’t.

  • avatar
    SCE to AUX

    These answers are leading to one conclusion: install an OEM clutch with a new flywheel, pressure plate, and throwout bearing, and make sure there are no leaks in the vicinity.

    My two experiences with replacing clutches yielded less than satisfactory results, probably because I didn’t go with the OEM product.

  • avatar
    heavy handle

    Here’s the deal. You went with an aftermarket clutch kit to save a few bucks, and now you know why it was cheaper.

    Lesson learned (I hope).

    Either live with it or pay to have it done right.

  • avatar

    Search on for this issue. It is common known issue with “oem spec” exedy replacement clutches. As much as they say they are, they are not the same as OEM. You are better off going with an ACT or some other aftermarket unit.

    I had a 2005 Saab 92x Aero for 8 years and replaced the clutch with one of these. I had the exact same issue. Luckily, for me, it smoothed out after about 500 miles or so, but was very jittery at first, to the point of stalling the car the first time I tried to drive away. The shop (EFI Logics in Danbury, CT) that did the install warned me about the issue ahead of time (I had purchased the clutch myself, not through them….they are great!) but I wasnt prepared for how bad it was.

    Spend the extra $$$ on a good aftermarket clutch and you’ll be all set. You can get one that feels just like stock, and don’t get one with too much additional clamping force, as you want the clutch to slip before your transmission grinds itself into 1000 pieces, as those are the weak point in WRXs.

    Good luck.

  • avatar

    Although it is possible, I highly doubt you received two faulty Exedy clutch kits. I’ve had nothing but great results with countless Exedy and ACT set-ups over the years.

    I would suspect the culprit is an error in the machining of the flywheel. If you have the box dropped a 3rd time; replace the flywheel, do not machine (as stated above).

    Lateral play at the input shaft can cause some chatter, inquire if the pilot bearing was touched. Either way have it r&r again.

    I have successfully used gearfluids to absorb clutch system vibrations in BMWs. I believe back then I used a cocktail which included Redline Shockproof. **Extensive** research is requiredd here, you don’t want to select a thicker fluid that could potentially damage synchros/bearings.

    Goodluck and next time buy an Evo. :P

  • avatar

    60K is very short clutch life , even in a Hot Rod .

    Clutch judder is usually caused by flywheel surface and / or bad mounts .

    When re surfacing a flywheel it’s critical to _grind_ it smooth , not have it turned on a brake lathe .

    Some flywheels are too thin so re surfacing them only lasts a short time before they get heat cracks and hard spots .


  • avatar

    I had an issue like this after replacing a clutch on a Mustang. Pulled it all back apart, inspected everything and re torqued everything with a better torque wrench and the problem went away. Hope this helps.

  • avatar

    Someone didn’t learn how to drive with a (father, uncle, granddad) sitting in the right seat whacking their leg every time they started to ride the clutch.

    If you ride the clutch, not only will you wear the lining out chop chop, you can also overheat the flywheel surface and recutting it may not provide the kind of friction surface needed.

    I would also question whether the shop remachined the friction surface on the flywheel correctly. For example, if the OEM surface was Blanchard ground, turning on a lathe ain’t gonna replicate that surface, and I doubt a “WRX specialist” having a Blanchard grinder on hand.

    If the OP knows how to drive a standard trans correctly, then the original owner doesn’t.

    Lesson to be learned: Don’t ride the clutch!

  • avatar

    Fuk automatic transmissions.

    I’ve never had to do anything to any manual clutch tranny vehicle (save gear oil drain/fill at maybe 80k to 100k intervals) until MAYBE the 125,000 mike mark (and often well past that).

    The U.S. and Americans in that they prefer automatic sh!tboxes to manuals, p!ss water Budweiser or Miller to actually drinkable beer, and baseball and American Football to soccer and hockey.

    • 0 avatar

      I rekun we also perfur sisters ovur cuzins. Git r dun.

      Transmission preference is not universal. Believe it or not, some people even like BOTH!

      But I’m glad we could transition this conversation from clutch/drive train woes to sports preferences. Thank you for that.

    • 0 avatar

      Two out of three ain’t bad, Deadweight. You can keep the soccer and hockey, though.

  • avatar
    Big Al From 'Murica

    My old Miata did this. The fix was an Italian tune up that really abused the clutch. Probably bad for the clutch in that I really got it hot, but as it was RWD and the replacement procedure didn’t start with “step one: remove engine from vehicle” I was willing to roll the dice. Never had any trouble out of it after that.

  • avatar

    I side with those who feel that having the flywheel refaced contributed you the woes with the new clutch. First, the OP mentioned that he’d had considerable trouble with the clutch slipping in Third. It wasn’t just slipping in Third, it was slipping in every gear, you just noticed it the most in Third. That flywheel got hot, very hot. Worst case, it warped slightly, best case it had one heck of a lot of glaze on it. Either way, a replacement would have been a better bet to my mind.

    And an OEM disc and pressure plate for good measure.

  • avatar

    I have a 2006 WRX. Had the clutch replaced at a local tuner shop with an Exedy OEM kit bought on Amazon. By the way, Exedy _is_ the OEM for Subaru clutches.

    They resurfaced the flywheel (not recommended by Subaru). Tons of vibration and noise at certain RPMs. The shop was adamant that the resurfaced flywheel was not the issue. I made them replace it with a new OEM flywheel, under the agreement that if this resolved the problem, they would pay for it, and if it didn’t, I would.

    The new OEM flywheel (about $350 from Subaru) fixed it, sure enough. Car drives like new.

  • avatar

    Sound like my two C6 Corvettes new from the factory. I hated their clutches. And I drove rigs all my life…

  • avatar

    Maybe it does still need more break-in, and you’re so easy on the clutch that it’s happening very slowly. When I ride with some people, I don’t see how I could possibly put as much wear on a clutch in 2000 km as they do in 100 km.

  • avatar

    Back when I was managing an auto shop one of our customers bought his newly licensed son a Scirocco. He ruined three clutches in a month. And I mean ruined. Car would not move at all the clutch slipped totally.
    Finally I had the schedule aligned with some time and went for a drive with the young man. He did not know the shift pattern and was starting off from a stop in 3rd gear.
    When that was sorted out clutch lasted many years.

    Also oil seals, crankshaft and trans input shaft, last about 1 1/2 clutches. We always replaced them when the clutch was replaced. Sometimes customers would protest “But it’s not leaking now”.
    I explained that 99% of the time it will leak soon and ruin the new clutch.
    There’s the old choice:
    You can get it done,

    Pick Two

  • avatar

    This reminds me of two cars I had long in the past with clutch chatter/shudder. Both were VW Type 1’a (orginal beetles). The first I didn’t keep long. The second, I bought new in 1973. It shuddered right from day 1. VW’s “warranty” didn’t cover this apparently. The clutch started to slip before the car hit 50,000 mi. So I bought a new disc and pressure plate and installed it in my driveway. An easy DIY job on the VW, a couple of hours to remove the engine, and a couple more to put it back in. All I did was dress the flywheel face with emery to break the glaze. Smooth as silk afterwards. I have done one other clutch job on an FWD car, a much bigger job, with no shudder. After many years as a mechanical engineer and DIY mechanic, I believe that the shudder can only be caused by a problem with either the pressure plate or flywheel. On the VW, the disc spring had broken, obviously defective from the factory. this made the pressure plate unsymmetrical. But an uneven distribution of the friction material deposits (glaze) on the flywheel face could do this or an improper finishing of the face. BTW, the dressing with emery is radial, across the direction of sliding. You do both the flywheel and the pressure plate faces.

    After installing a new friction disc, it needs to be bedded in. This is similar to bedding in new brake pads/linings. You need to get it hot, but not too hot. If you don’t get this right, then the clutch could behave badly from then on. During this process, some of the friction lining material is deposited on the mating faces of the flywheel and pressure plate. This must be smoothly and evenly distributed. Once a clutch starts to shudder, that is impossible. The buildup is uneven, resulting in a grab-release cycle each rotation of slip.

    I just thought of another reason for this. During installation, the mechanic may get some contamination on the friction lining of the disc. This could have the same effect.

    Concluding, I think that the installation procedure could have as much or more effect than defective flywheel or pressure plate. The original clutch for the OP likely was abused, witness the early failure. The subsequent problem MAY have come from the resurfacing/lack of replacement of the flywheel and/or installation procedure. The fact that the clutch didn’t shudder before replacement indicates the latter.

    I have a lot of experience with industrial brakes. We sometimes have issues with the friction materials not behaving properly. I jokingly say that predicting friction performance is Voodoo, because there are many variables involved. Temperature, humidity, and contamination are key, as are the condition of the mating surface. Too smooth is bad, too rough is bad, too thick a glaze layer is bad, etc.

  • avatar

    Way back when, having a Corvair Corsa, with clutch shudder after ‘my’ replacement – my shop teacher lent me an alignment tool. He told me the shudder was because the clutch was slightly, off center with the flywheel and transmission shaft.

  • avatar

    Hey guys, original poster here.

    I originally sent this through a few months ago, but sadly Sajeev wasn’t able to run it sooner. But this means that I can clear up a few things here.

    I can shed some light on why the original clutch needed to be replaced at 94,000km. Believe it or not, but the car was owned by a Christian rock-loving, mother of two. But this family clearly had petrol running in their veins – they had previously owned many T-56 equipped Holden V8s, and the WRX was replaced with a Legacy GT Spec B. But the car was driven mostly around town in stop-start traffic when I’d bought it at 67,000km. So that meant the wear would’ve been higher than a more lightly driven freeway car. Who knows, maybe the original owner enjoyed launching her WRX?

    Second of all, I learnt manual on this car. While I did burn the clutch a bit at first, I was fine by the 2nd week of driving it. My driving mostly consisted of driving to and from work in urban areas.

    The biggest factor to the early clutch replacement would be the dyno tune on the car. With a bigger turbo back 3″ system, it went up from 125awkW to 168awkW. When the clutch was starting to go, it was occasionally chattering when taking off at the lights (this is probably down to flywheel abuse), and the clutch was starting to slip in WOT in third gear. This is often symptomatic of a tuned car, on a OEM spec clutch, when you ask the clutch to deal with 35% more power. If I’d reverted to the stock tune, the slipping in 3rd gear would’ve disappeared with less power. I could’ve easily gotten another 10-20k km if the car wasn’t modified.

    The slipping wasn’t massive, and you would barely notice it in normal driving, but I couldn’t be bothered dealing with a slipping clutch in a performance car.

    Let it be known that while I’m not the easiest driver in the world, I do have mechanical sympathy. But if I’m going to have a turbo rally bred car, there will be the occasional 4k RPM launch, where I’ll feather the clutch a tiny bit to avoid sending a massive shock through the gearbox. The other posters are correct, Subarus do have weak clutches to prevent people dumping the clutch and breaking gearboxes.

    In short (or TL:DR), car driven in 95% urban situations, used to learn manual, then moar BOOST and hard driving equals short clutch life.


    Anyway, moving on – in the time before this was posted, there was a solution to this problem.

    With the flywheel machining issue, my mechanic (a trusted WRX and EVO specialist in Adelaide) was replacing the used flywheel with a pre-machined, ready to go flywheel. They are a high turnover garage and can’t have a car sitting in a hoist for 2-3 hours while a flywheel is machined. Unless they were all warped, bad flywheels, this narrows this out.

    After the issues with the 2nd replacement clutch, I went back and my mechanic said he was going to cover the costs and pay for an OEM clutch direct from Subaru, rather than Exedy. I was happy with this outcome as I didn’t want another Exedy clutch going in, and either did my mechanic – after forum searches, this seemed to the be common fix.

    However, when I went back to pick up the car, my mechanic said he’d looked at the Exedy and Subaru clutch, and advised me he didn’t think it would make a difference as they looked identical. The internet says otherwise (AND WE BELIEVE EVERYTHING ON THE INTERNET!), but he seemed convinced that they’d be the same.

    In the end, they put an Exedy HD clutch in, which fixed it! There was no shuddering. However, this created other problems, as the clutch was noticeably stiffer (a bitch to drive in traffic…), and I never wanted a HD clutch as they apparently destroy stock 5 speed Subaru gearboxes.

    Sounds like it was the Exedy clutch not being right, but lesson learned, demand OEM or go through this again.

    It was pretty annoying they put in the HD clutch without consulting me, but it didn’t really matter, because in the end I sold the car about a month later to someone interstate, who was happy to pay a premium due to the condition and mileage of the car. They ended up driving it back 2200km/1400 miles back home. Go figure.

    I ended up buying a Legacy GT which recently had the clutch replaced at 146,000km.

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