transmission symptoms (?) [c900]

Hi,

My 1992 900 (NA) has been running pretty well lately, but then about a month ago it left me stranded, unwilling to go into either 1st or 2nd gear. I had it towed, and sure enough it was a problem with the shift linkage. Which they fixed.

After that, the shifter felt like new, and all was well for one week.

Then I was out of the country for two weeks, during which the car just sat in the driveway.

Upon my return, the car still runs, but suddenly has some rather interesting symptoms:

  1. Upon starting from a dead stop (in either 1st or reverse), there is a slipping sensation just as the clutch engages (feels like starting on wet or icy pavement). There might be a noise coming from the engine compartment when this happens, but I'm not sure about that yet.

  1. Although shifting up through the gears from 1-5 works fine, shifting down from 3 into 2 causes grinding, as if there is a problem with the synchro. Shifting down from 5 to 4 and 4 to 3 works fine.

I would greatly appreciate any thoughts as to what might be going on here.

Thanks,

John

Reply to
John B
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Don't bother asking... These guys are a bunch of good ol boys and only talt to themselves.

Reply to
Xanadu

John B (rotten_NOSPAM snipped-for-privacy@ccil.org) gurgled happily, sounding much like they were saying :

Sounding very like a clutch problem. It's a dead easy job to change on a c900, especially a non-turbo.

Reply to
Adrian

Thanks for the reply.

If it is a clutch problem, that would indeed be welcome news. But can clutch failure explain the grinding when shifting down into 2nd gear?

John

Reply to
John B

John B (rotten_NOSPAM snipped-for-privacy@ccil.org) gurgled happily, sounding much like they were saying :

Absolutely, if it's not releasing properly/fully.

Reply to
Adrian

I think the clutch theory is pretty solid. Further supporting evidence: A couple times, I think the clutch was catching a little bit even when the pedal was depressed. And also, there are the noises. With the car idling in neutral, clutch engaged, I heard some relatively loud rattling from the engine compartment. I popped the hood and got out to listen. The noise was intermittent, and (as far as I could tell) was coming from the clutch housing. It sounds like something has broken loose in there, and is getting thrown around as the clutch spins.

I think I'll open up the clutch on Saturday and have a look. I've never done this before, so it should be interesting. I ordered a clutch spacer tool, but I doubt it will arrive before this weekend.

If I do take the clutch apart to investigate, can I put it back together without any new parts? Or will it be necessary to have replacements in advance? The tricky thing is that I won't know what needs to be replaced until I open it up.

John

Reply to
John B

John B (rotten_NOSPAM snipped-for-privacy@ccil.org) gurgled happily, sounding much like they were saying :

I believe you can do without - just use a solid thick wire - I gather an HT lead's too thick, so maybe some domestic T&E...?

Sounds like the release bearing either on the way out or worn through the fingers on the pressure plate.

Reply to
Adrian

I'm surprised to be having clutch problems, as the clutch was replaced about

45k miles ago. I did have to abuse the clutch a little to get the car onto the tow truck when the shift linkage failed (picture a car that won't go into 1st or 2nd, a flatbed tow truck, and badly rusted towing eyelets), but I think it should have just been burning friction material rather than damaging any bearings.

John

Reply to
John B

John B (rotten_NOSPAM snipped-for-privacy@ccil.org) gurgled happily, sounding much like they were saying :

All of it? Release bearing plus three piece kit? Or just the friction plate?

Reply to
Adrian

I had assumed it was a complete kit, but now that you mention it I guess I don't know for sure- it was awhile ago, and I doubt I can find the records. Anyway, I'm excited to open it up and see what's going on.

John

Reply to
John B

Hi John, if you do not yet have the spacer tool, and assuming the clutch is still functional enough:

I used the outside part of a bicicle brake cable, you know the black part that is basically wound metal wire. Its thickness is right to insert into the clutch housing, and because it is metal it is strong enough to keep the clutch fingers depressed. Do you have a manual of some sort? It would help tremendously! Hope that helps, Richard.

Reply to
Richard

I'll probably look around the house for something of the right thickness and length. If I can't find anything I might have to buy some wire.

I do have the Bentley manual.

Thanks,

John

Reply to
John B

I took the clutch apart today. I used some heavy copper electrical wire on the pressure plate. It took me a little while to work it in (very stiff), but it did the job.

Everything inside looked OK to me, but of course this is the first time I've taken one of these apart. I've posted some pictures here:

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After I put it all back together I took a test drive. First off, I'm pleased to report that the clutch works normally- this probably means that I took things apart and put them back together again the right way.

The second thing is that the problems I was originally complaining about in this thread did not manifest themselves during my 10-minute test drive, despite the fact that I did not replace any parts today.

I think that if it is a real problem, it will start acting up again sooner or later.

Thanks for the suggestions, and let me know if you see anything amiss in the photos.

John

Reply to
John B

John B (rotten_NOSPAM snipped-for-privacy@ccil.org) gurgled happily, sounding much like they were saying :

Certainly all looks OK to me, but it's interesting that you've got an AP pressure plate and Sachs friction plate - so last time it was done, it was probably done on the cheap, with only the friction plate replaced. OTOH, the pressure plate looks newer than the friction plate...

Nice ingenuity with the cranked screwdriver, btw...

Reply to
Adrian

Hi, I dont see anything wrong in the pics either. Did you bleed the clutch hydrolics? Maybe there was some air in there that made the clutch not disengage completely.

Another possiblility is the clutch master cylinder, maybe a tiny leak in the seal there?

Richard.

Reply to
Richard

Yeah, I think that the pressure plate and friction disc were both replaced. I don't think it's unusual to get an AP pressure plate with a Sachs disc-- see for example:

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(this is a 7-piece kit with AP pressure plate & Sachs disc). Based on what I've read, I still think the release bearing is the most likely suspect. If the clutch starts acting up again, I'll put in a new release bearing and see how that works.

John

Reply to
John B

No, I didn't open or bleed the hydraulics.

Certainly a possibility, although the master should be in good shape. I rebuilt it a couple years ago after the spring inside it broke.

John

Reply to
John B

It seems like something is acting up again. A couple times on the way to work this morning, the following happened: just as the car was rolling to a stop (car in 1st or 2nd gear, clutch pedal depressed), the car suddenly (and loudly) seemed as if it had hit something.

Working on the theory that the release bearing is failing: In this situation the release bearing is under load, and it may be briefly seizing... Oh wait, that doesn't make sense, if the clutch is disengaged then the pressure plate isn't connected to the transmission. Maybe I was hearing/feeling the engine suddenly decelerating, rather than the car itself?

Any theories? I'm still tempted to just order a release bearing to see if that fixes things.

John

Reply to
John B

Ok, this loud shuddering thing happened again, and I have a new theory: warped pressure plate and/or flywheel. At this point I'm tempted to just replace everything and be done with it.

John

Reply to
John B

So this weekend, I did a complete clutch job (replaced pressure plate, clutch disc, pilot bearing, release bearing, clutch shaft seals, slave cylinder, and resurfaced flywheel). Also replaced the rear main seal. As far as I can tell, my problems are solved (clutch functioned normally and quietly). Here are a couple notes for posterity:

  1. Putting the rear main seal in without the special tool was a bit tricky, and took some improvising. I ended up just getting the seal started by hand, and then putting the flywheel over it and cross-tightening a few of the bolts all the way down (a little at a time). I took the flywheel off, and found the seal was pressed in most of the way, and it was perfectly even. I finished it off by putting the old seal over the new seal, putting a block of wood over the old seal, and gently prying with a pry bar until it was evenly seated. The new seal ended up seated a little deeper than I wanted, but I think it worked out OK, no major oil leaks (yet anyway).
  2. I had some serious problems with the slave cylinder. After installing the new slave cylinder (from eeuroparts.com), the clutch worked one time before spewing hydraulic fluid everywhere. When I took it apart I found that the seal on the outside of the piston was broken. So I tried to put the old slave cylinder back in, but the big seal at the base of the slave housing ruptured in the process, resulting in more hydraulic fluid everywhere.

So I took it apart yet again, and transfered the old around-the-piston seal from the old slave and used it to replace the broken seal on the new slave. Put it all together again, and... more hydraulic fluid everywhere. After taking it apart again, it seems that the old seal probably broke when I put the cylinder together (not surprising, the old seal was really stretched out). I was getting rather depressed at this point, but then I remembered that there is another small seal *inside* the piston. So I cannibalized that seal from the old cylinder (it was in good shape), put it around the piston of the new cylinder, and put it together for the 5th (?) time. Miraculously, it worked perfectly, and I was a very happy man. Too bad my driveway is now a toxic chemical dump...

John

Reply to
John B

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