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Techniques to test condition of clutch?

Discussion in 'Technical Q&A' started by rob lay, Feb 26, 2004.

  1. rob lay

    rob lay Administrator
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    Dec 1, 2000
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    I was asking Mike at Norwoods how you can know the condition of your clutch before it obviously starts slipping. You know, 4th gear and RPM's go to 7k, but car isn't going faster. :)

    Mike said one technique is to try rolling the car from 4th gear. If clutch is bad then it will spin up the RPM's and won't stall. If clutch is OK then it will grab and stall the car.

    What other techniques are there? Anyway you can tell just by pedal feel or placement?

    Thanks,
    rob
     
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  3. Mule

    Mule F1 Rookie
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    A completely non-scientific quick check on the 328 is to see if the clutch pedal and the brake pedal are at the same height. Usually means that the clutch has life in it.
     
  4. rob lay

    rob lay Administrator
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    Which way would it be if it's getting towards the end of it's life? Higher or lower than the brake pedal?
     
  5. 308GTS

    308GTS Formula 3

    Dec 27, 2001
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    Higher off of the ground. The higher the pedal the more the wear. On a 308 this can be deceiving the pedal can be high but you can still have 75% of your clutch life left. Just adjust it and then readjust as needed.
     
  6. Bob308GTS

    Bob308GTS Formula 3

    Sep 26, 2001
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    A quick way to check for slipage, with the engine at a normal idle, engage 5th gear, with right foot on brake slowly engage clutch, engine should stop if there is no slipage
     
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  8. Mule

    Mule F1 Rookie
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    Hmmm... my mechanic says it would be lower (farther from the driver) as it wears on a 328. I would think it is the same as the 308. Don't know.

    From my experience, when I bought the car, the pedals were level. Now the clutch is about 1/2 inch lower (farther from driver) than before.

    Also, new idea - Feel if the clutch engages as soon as you depress it or closer to when the pedal is near the floor. The clutch should start engaging as soon as the pedal starts going down. If it does not engage until it is almost pressed all the way in, that would indicate wear.
     
  9. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
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    The more the clutch wears the higher the clutch pedal will be off of the floor on a 308, guaranteed. When I say higher I mean higher relative to the floor not closer to the floor. Believe me I have adjusted enough of these.
     
  10. Auraraptor

    Auraraptor F1 World Champ
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    Sep 25, 2002
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    My clutch engaged very high and they said it was mostlikly a bad clutch. They couldnt adjust it so it grabed further down.
     
  11. Mule

    Mule F1 Rookie
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    I believe you. I will ask my guy again (and if he has some amplifying information).
     
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  13. wolftalk

    wolftalk Formula Junior

    Jan 27, 2004
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    #10 wolftalk, Feb 28, 2004
    Last edited by a moderator: Sep 7, 2017
    since I got misdirected a long time ago looking at archive posts about clutches, I'll tack on to this thread the comment that the clutch setup on an earlier 308 is different from the 308qv and 328. The change occured sometime around early 1981. also, some people retrofitted because the newer setup has much lighter clutch effort.

    in both setups, the clutch release fingers at the point of contact with
    the throwout bearing move away from the flywheel as the clutch disc wears. Due to a lever arm on the bell housing, this translates into the clutch cable shifting towards the rear of the car.

    on the newer setup, this pivots the clutch pedal pad end further away from the floor like 308GTS said, and you periodically make adjusts to lower the pedal back down

    on the earlier setup, clutch wear chews up the free play necessary to keep the clutch from slipping...because on the early setup the pedal cannot raise - there is a stop preventing it. If you use up all the free play, the pedal stop and cable prevent the pressure plate from completely clamping the clutch disc, and you get slip and accelerated clutch wear.

    note there is no free play adjust on the later setup...the clutch pedal just keeps raising as the clutch wears.

    to make sense of the above, look at the tsb's on thread:
    [thread]6785[/thread]

    if you have a 328, 308qv, or a later 308 with the newer clutch setup, and the clutch pedal is getting lower to the floor, the most likely cause is the clutch cable fraying, snapping, and stretching. check especially where the cable enters the engine area from the tube under the driver floorpan. could also be the adjust points aren't locked down and are unscrewing themselves.

    The pedal can't get lower to the floor on the old setup unless a spring on the clutch pedal is busted. that spring pulls the pedal up against the stop (and helps move the throwout bearing away from the release fingers, which is the freeplay you need).

    wrt to where in the pedal travel the clutch engages, I don't think you can change that much on the new setup (assuming you want the clutch and brake pedals even). There is never any slack in the clutch cable, so the clutch always does it's thing near the top of the pedal travel. The only variable is the position of the level arm on the bell housing. referring to the attached pic, I guess the more horizontal (2) becomes, the more travel the pedal may need to make to move (6) the same distance. Which I guess implies that you can tell how worn the clutch is by how much longer (6) needs to be to maintain the 40-45mm spacing shown. would be nice if that could be quantified.

    Also, a fraying clutch cable will stretch under load, which will move the engage point lower.

    on the old setup, you can vary the clutch engage point a lot by changing the amount of free play (in effect, make slack in the clutch cable). too much free play, though, and you never completely disengage the clutch.
    Image Unavailable, Please Login
     
  14. thecarreaper

    thecarreaper F1 World Champ
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    yep, bump so i can find this one too.
     
  15. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    Rob, if you are talking about your 355, the higher the clutch pedal goes before it engages the closer you are to replacing it. If it engages shortly before it stops coming up it's circling tha drain. A good test for any car is to get it near peak torque in a higher gear (4th good for 355) at a cruise and stand on it. thats about the most load you can put on it without being abusive. The motor should not sound as though it has suddenly picked up speed and then slowed down, or the tach has not jumped up then settled back down.
     
  16. fatbillybob

    fatbillybob Two Time F1 World Champ
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    Aug 10, 2002
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    Sometimes the clutch is going before all the surface is gone. This is due to oil leaks and odd wear patterns. If you are inquiring for the 355 trackcar then I think it should be open and inspected as a matter of safety and routine maintenance. The clutch is only a 2 hr in out by this home mechanic. After every weekend I put my car on the lift and tighten every suspension bolt, look for shock leaks, inspect the undercarrage, tighten a-arm bolts, cv joint bolts, clutch internals (bolts to flywheel etc..) and regular tech items, I change T belt once a year with valve adjustment. here is why. 2 weeks ago on the track some guy broke a power steering line and oiled himself...he flipped his car. Today a guy lost a circlip in his gearbox and the axleshaft pulled out until it hit the bodywork. That saved him. He only spun at about 110mph and oiled the track. Another, guy today blew his motor and oiled the track again. Some other guy lost a piece of his car and I hit it. Luckily no damage. I could have lost a tire. Do yourself and your fellow racers a favor. Check your car and check it often.
     
  17. Rifledriver

    Rifledriver Two Time F1 World Champ

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    Very good advice and should be heeded by people tracking their street cars as well. A couple hours on the track is like a couple of years on the street.
     
  18. ferrarifixer

    ferrarifixer F1 Veteran
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    To test the efficiency of the clutch, accelerate at full throttle at whatever rpm makes the most torque...typically 66-75% of max rpm.

    Do this in a high gear but not top, 3rd can be ok, but the lower the gear, the easier the acceleration is and the less work it has to do.

    If revs flare under full torque load, then it's slipping. A smal stab on the pedal to provoke slip is ok occasionally, revs will flare only briefly and come back to steddy climb associated with speed climb.

    Most drivers will first notice slip while shifting under hard acceleration. If it gets this bad the load test will be easy to judge already and it's all over for Mr Fritzione...
     
  19. thecarreaper

    thecarreaper F1 World Champ
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    my clutch is toast. :( service records show it has about 15,000 miles on it. been searching the archives and found a thread on a GT4. time to call F.UK and get a kit and the Baum socket thingy :( the service records show a Daytona clutch, anyone know why you would put in a Daytona clutch? perhaps there are places that sell whole kits with the bearings ect included? i may just have a local shop refurb the old disc and buy a new pressure plate et al. :(
     
  20. Aircon

    Aircon Eight Time F1 World Champ

    Jun 23, 2003
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    Ok..here's a question. I'm guessing from what's been said here (and it's sort of what I've experienced in the past) that a clutch doesn't just fail immediately as it wears out but, rather, gradually and that you might notice a bit of a slip under full power, then as it wears more, you get more and more slipping under less and less power...soooooo...now for the question....how could a mate of mine's clutch start slipping over a period of maybe 10 gear changes (all moving...not stationary) to the point where the car won't drive at all? (i.e. slips too much to even take off in first again!) It's a carbon clutch if that makes any difference...no one seems to really have a clue on this in Aus. Anybody had this happen to them before?
     
  21. Doc

    Doc Formula Junior

    Sep 13, 2001
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    Could it just be way out of ajustment or could the lining be so much thicker than a stock clutch's that it never fully leaves the flywheel? I'm not a mechanic--just guessing.
     
  22. Aircon

    Aircon Eight Time F1 World Champ

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    But to go from working fine to not working at all in 3 mins? I can't even guess! :)
     
  23. Rifledriver

    Rifledriver Two Time F1 World Champ

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    In the earlier days of the 308s some thought that installing the Daytona clutch (same dimensionally) would make it last longer. I had a client that went through a clutch every 10k miles like clockwork. We tried one in his car and it did not last any longer but driving it was a pain. Pedal effort was very high due to the stronger pressure rating of the clutch.
     
  24. ferrarifixer

    ferrarifixer F1 Veteran
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    Aircon...what are you on about??

    You know that particular 360 N-GT Clutch is carbon and behaves nothing like a conventional clutch...plus...how can you say no-one knows anything, when you haven't asked??? And I know you know I'm doing the repairs.

    The clutch in question worked fine when it got back to the pits...because it had cooled down by then. When carbon clutches are slipped they generate huge heat, which has a negative effect on the friction levels.

    A good example of this was the Sandown 500, when front row HRT car (Kelly) fried his clutch at the start, but the safety car after a couple of laps allowed it to cool and he got going properly again.

    When you were in the car you refer to, it started to slip, was allowed, even provoked, to continue slipping until it became so hot it stopped gripping.

    Upon dismantling, the clutch "looks" fine. Simply inadequate clamping due to wear in the plates.

    The part I'm not able to explain is why carbon brakes need heat to grip, but why carbon clutches slip when too hot.

    It must be to do with the composition, but I'm unable to explain.
     
  25. Aircon

    Aircon Eight Time F1 World Champ

    Jun 23, 2003
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    I don't know that that's a terribly accurate representation of events, actually. What would I know though...I was only in the car. After a few laps of the clutch working perfectly well, it suddenly slipped under full power 3 or 4 times for a brief period, then the driver backed right off. From then on, it had no more drive...and no...even 1/2 and hour later, when you tried it in the pits, there was still no drive...hence, it can't be temperature related, can it? And if, as you say, it worked fine in the pits, (which isn't what you said on the day) then why did it start slipping in the first place? Surely you're not saying that this inadequte clamping went from ok to undriveable in one lap, are you? Hence, my comment that no one seems to know how these things work.
     
  26. ferrarifixer

    ferrarifixer F1 Veteran
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    You're living in cloud cuckoo land.

    The clutch worked fine in pit lane, once cool ie immediately after it had been recovered and after about 30 min from when it stopped on track. I drove the car up and down 3 times, and advised that no fault was apparent, but that there was every chance the same would occur next time out.

    The driver said he thought it may have been wheelspin. By the time he realised it wasn't, drive was lost.

    The clamping load is adequate for rolling around in first gear when cool, but not for delivering 450+BHP through hot slicks.

    I'm not going to enter any more debate with you. You should be a mechanic yourself maybe?
     
  27. Aircon

    Aircon Eight Time F1 World Champ

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    At least I'd be a good one.
     
  28. thecarreaper

    thecarreaper F1 World Champ
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    makes sense. the clutch feels TOTALLY different than the one in the 78GTS i had. it was engaging very high on the pedal and slipping if anything higher than 2nd. i have adjusted it all i can. now it will engage closer to the floor, and the pedal height relative to the brake pedal has not changed. car has no oil leaks either. guy drove it 2 weeks ago to his job and took pics ect and said it drove fine. Murphy's law i guess. i am not crying about what the car needs, i just want to drive the darn thing after waiting this long for a nice red GTB. :( :( :( i wonder why the clutch would wear out so fast?
     

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