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I have a Subaru STI 2009 with 180k kilometers on it a very hard clutch, closer to a truck than a usual car. It works fine and has been that way for at least the two years I've had the car but it is so hard that I wore through two master cylinders within the last year and if I remember correctly the Western Star 4900 I tried last year had a slightly softer clutch.

I also tried another, more recent, STI and the clutch was hard for a normal car but nothing like mine.

Now after watching a few clutch videos I wonder if simply opening up the clutch and greasing the throwout bearing axle and other sliding parts could solve, or at least help with my issue?

There is no rattling noise when I use the clutch, and it works great apart from the fact that is is pretty much impossible to do a clean start without any vibration. It feels somewhere in between that other STI clutch I've tried and a race clutch I tried a few years back on a Jetta VR6. The race clutch had more vibration but was softer than my clutch.

A possibility would be that a previous owner modified the pressure plate for a heavier one but I don't know how I could verify that other than opening it up.

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  • Is your clutch stock or aftermarket?
    – Huesmann
    Jul 3, 2019 at 13:47
  • I don't know, I did not change it but maybe a previous owner did.
    – Johnride
    Jul 4, 2019 at 18:15

3 Answers 3

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Don't try greasing anything inside the bell housing. Grease will get thrown onto the friction plate and cause you problems.

If the pressure plate is faulty or a previous owner had a heavier plate fitted then the only cure is to change the plate for a "normal" one.

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  • Of course I'm not talking about dumping a pound of grease in there just a thin layer as instructed in this video youtu.be/YeIUEV_ua9Q?t=939 . With good quality (like brake hi-temp?) grease I doubt it would ruin the friction surfaces. I'll be expecting to replace the pressure plate though following your advice.
    – Johnride
    Jul 1, 2019 at 16:12
  • Unfortunately, there isn't a way to troubleshoot a lot of clutch issues without opening it up. I don't know much about your clutch (most of my experience with clutches is on motorcycles), but it could be that something is torqued beyond spec. I know some clutch designs can be very picky about the torque values. That's the only thing i can think of that may not present any visual signs, but again, you'll have to open it to check.
    – kyle_engineer
    Jul 1, 2019 at 17:25
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It is possible that you have a warped pressure plate which prevents smooth engagement of the driven plate.

It is also possible that your driven plate is exceptionally hard, or lacks all the springs in it that it was designed to have. (That is it is not as soft as it should be.)

Those are just theories, and if the problem bothers you enough, you get to decide whether you should take it to a transmission shop for diagnostics.

I do not understand why you went through two master cylinders with this problem. Is it that there is lots of vibration at clutch engagement?

Unfortunately, with clutches, other than linkages and engagement cylinders, most of the guts are inside the bell housing. If you were to open it up to "lubricate" things, I would rather open it up to inspect the components. Once you have that kind of labor, simply replacing the components may not be that much more, and will rule out the two plates which are likely causing your problems.

To be sure, is the clutch hard upon engagement, or heard to release? If hard to release, that could be a different set of issues which I have not specifically addressed here.

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    I don't think the OP is asking about clutch engagement, but rather how stiff the clutch pedal is to depress.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Jul 1, 2019 at 19:28
  • That's right. The rough engagement is another issue that bothers me less since it is not that bad and I think that a softer pedal will help me control engagement. But your theory is interesting I'll inspect all components when I get to open it up.
    – Johnride
    Jul 2, 2019 at 9:43
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I would take a look at the slave cylinder. If you are wearing out master cylinders something is not right.

It may be the slave cylinder has worn away a pocket in the release lever. This is supposed to be lubricated with special grease. It's not easy to get to, but it is external to the transmission.

Check the interface to see if there is rust or abnormal wear on the release lever.

enter image description here

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  • If I remember correctly the slave was changed the first time I changed the master. But I'll inspect it as my memory is really unclear about this. And in my case it's rather easy to get to, just have to remove the intercooler.
    – Johnride
    Jul 2, 2019 at 9:43

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