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Car mechanics, step in here for a second...


Scruit

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Car is a 2005 Subaru Legacy Gt 5MT AWD. 

 

Driving the other day I had a tough time getting the car out of gear for a 2-3 shift. From that point I couldn't engage any gears with the engine running. Engine off, I can select all gears and can hear them all click into place properly, so the trans is fine. There was no unusual noise associated with the failure. Had driven about 10 miles on the freeway and changed gears from 5-4-3-2 on the offramp, then after accelerating in 2nd switching up to 3 felt like clutchless shifting (when you mistime it and you feel a lot of drag on disengagement, bot not any kind of grinding or catching)

Clutch pedal feels normal. Fluid level good. Not leaking. Slave cylinder moves the shift fork, and does not retract while the pedal is held down. Pumping the pedal quickly does not increase the travel of the slave cylinder. Last clutch and fluid replacement was about 2 years ago with genuine Subaru parts.

If I start the engine with the trans in 1st and the clutch pedal to the floor the car lurches as if the clutch is not pressed (although the clutch interlock would normally prevents the lurch, because the pedal is being pressed the interlock is disengage)

It is sitting at the dealership right now. Any ideas?

I have considered (and rejected) the following:

- No hydraulic fluid: Slave cylinder moves and fluid level is normal. No external leaks noted.
- Air in hydraulic line: System has not been opened in 2 years. Air could only get through a hole, which would leak under pressure rather than absorb air.
- Pressure plate/flywheel/clutch plates stuck: Maybe if the car had sat for a while, but it's my DD and was driving at the time of failure.
- Master or slave cylinder piston seal failure: The slave cylinder moves when I press the clutch and does not retract until I release the pedal. I would expect a major piston seal failure to prevent the slave from moving at all, and a minor failure to see the piston retract slowly.

- Clutch pedal height adjustment (under dash) came loose, moving biting point down bleow the carpet: This is my current prime suspect. None of my observations rule this out. I adjusted this about 2 years ago, it's possible the adjustment has wandered.


The car is sitting at the subaru dealer waiting for them to take a look "early in the week". I will call in there in the morning and give them the above observations to help their tech, and to manually check the pedal height adjustment myself. I also want to make sure I catch on video that the trans currently select all gears normally while the engine is off - don't want someone to try to He-Man it into gear and snap a shift fork and blame that on me.

Video of slave cylinder test (as of 21:50 ET on 1/12/2014 this video was still uploading, so won't be visible for about 30 mins)

Edited by Scruit
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Being you are able to select gears with the engine off I don't suspect an internal transmission issue. My guess is it is between the slave cylinder and trans input shaft....clutch fork,throw out bearing or pressure plate. This is purely a guess.

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What could be wrong with the TOB?  It is not creating noise (either rotational with or inline with pedal).  The shift fork is moving.  Can the TOB become disconnected from the shift fork?

Edited by Scruit
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What could be wrong with the TOB?  It is not creating noise (either rotational with or inline with pedal).  The shift fork is moving.  Can the TOB become disconnected from the shift fork?

 

This would be my guess... all of your symptoms suggest that you are not disengaging your clutch, all clutch components external to the bellhousing you've accounted for... all that is left that i can think of is a cracked clutch fork, or dislodged throwout bearing... 

Edited by magley64
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Dealer says the problem is inside the bellhousing, so I just authorized taking the trans out. While it is out I'll have them do the rear main seal. They suspect the clutch pressure plate or tob. I asked them to check the pedal height adjustment before pulling the trans.

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Sounds like a clutch to me, though. Did you have the flywheel resurfaced when they replaced the clutch? Glazed flywheels are hell on friction plates.

 

Worn friction plate would get you to a "non-engaged" clutch condition more than a "permanently engaged" condition though, wouldn't it? 

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The failure mode of "won't disengage" strikes me as more of a mechanical failure than an expected-end-of-service-life thing.

So the fork moves normally, we can see that. The fork pushes the tob into the fingers of the pressure plate. Are the pressure plater fingers broken? Are they bent? Is the tob not being moved by the fork? Is the fork bent?

No clue right now. A full clutch job should fix it but I have asked for an explanation of the failure, not just a fix.

I wish the bellhousing had an inspection port on it. Oh well.

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Yup. Looks likely. I wonder if the broken finger would be expected to make some kind of noise as it came loose near the spinning clutch or if it fortuitously has fallen to some safe place. After the clutch failed I limped about a mile off the freeway to my office. Never heard any noise.

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It could be that a finger broke off and wedged itself between the plate and disk which is causing to be "engaged" all the time regardless of what you're doing with the pedal itself.   :dunno:

Edited by r1crusher
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I don't remember if cars have springs in the clutch disc but in heavy duty clutches they do and will break and jam up the clutch causing similar issues.

 

Yeah, ISTR this clutch has the regular fingers that hook up to the TOB, and it has 4 springs.  Anyone of those could have failed and jammed it up.

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Interesting...

 

Went over to the dealership to check out the car.  They have it all put back together and have even had it out on a test drive.   I requested the old parts back and when I got to the service bay I saw the parts were laid out ready for me to pick up tomorrow (car is not quite ready).

 

 

There is nothing visibly wrong with the clutch...   The friction plate appears to be about 75% of the way through it's service life (when I replaced the first one at ~65k miles the rivets on the pressure plate side were scraped clean - there is about 1mm material left above the rivet head on this one).  No broken fingers, no broken springs.  I'll try to get the final word from the tech tomorrow, but as it sits right now the old clutch appears to be serviceable - no clue why it wouldn't disengage.  The TOB is intact although the bearings are showing the beginnings of Subaru TOB disease (rough bearings at 60-70k that will eventually lead to chirping then failure).  The TOB, like the clutch, appears to be serviceable but close to end-of-life.  The TOB had about 5k left on it, so the clutch job would have come due in the next 3 months for my volume of driving, so the clutch service was definitely needed.

 

I have not seen the bill yet but I was not asked to approve a flywheel or any other components.  

 

Just confused right now as I have no current explanation for the failure-to-disengage.

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BTW, I got my clutch from an online subaru dealership 4 years ago (will name it if I can find which one) when I did the first clutch job. This Subaru tech today noted that I had a "inferior brand" and was "not happy with the clutch I put in there". The hub on the friction plate is labelled "Subaru" and "Sachs Germany".

I made the call a long time ago that I'm keeping this car indefinitely so even though it's nearly 10 years old I use dealer parts on it. I though I was putting a Subaru clutch in there. Is Sachs not the OEM manufacturer?

 

The clutch I put in at 65k was this:

DescriptionUnit priceQtyAmountSubaru Legacy GT O.E.M. Clutch Kit
Item# $285.00 USD1$285.00 USD
Fred Beans Parts. 2009-11-29.
I thought this was a Subaru clutch... is it not?

Could this have been a NA clutch? I just searched for Sachs Germany clutch and found this:

                            Fits the following 2005 Subaru Legacy submodels:

                                                        
  • 2005: GT Limited; 4 Cyl 2.5L; "Naturally Aspirated"


 

I'll be pissed if that is what has happened.  I thought all the Legacy GT were turbo.  It may be that I selected the wrong clutch 4 years ago and burned it up on an engine that was too powerful for it.

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So I got my car back.  Cost me $1250.

 

The tech had no solid reason for the failure except that the pressure plate "must have gone".  The pressure plate show no signs of any kind of damage, just that it's old.  The friction plate and throwout bearing were due to be replaced, but there was no explanation why why the clutch refused to disengage.

 

I did notice that the new clutch is so damn light that when I first got in I thought the pedal wasn't even hooked up.  The factory and first replacement clutches were both very heavy.  This one is so light I'm having to get used to it like driving a different car.

 

The concern about the clutch brand was a non-issue.  Tech said that he though the old clutch should have been something other than Sachs, but when he got the new clutch from parts it was identical. 

 

 

So, at the end of the day, I have no clue what happened other than I did my next clutch swap about 5k miles sooner than I otherwise would have.  Huh.

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The fork pushes the TOB forward into the pressure plate fingers.  The TOB clips to the fork and has a rotating hub that contacts the fingers.

 

I'm confused about why this clutch is so much lighter than my last one.  I can push the clutch all the way in with two fingers.  Almost with one.  Previously I couldn't do that.   Both original clutch and first replacement.  Wierd.

Edited by Scruit
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Because they replaced the slave cylinder, which was the actual problem? Make another identical video and see if the distance it travels is the same.

Edited by Gump
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