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Thread: Clutch slip

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    Clutch slip

    Morning guys
    Regrettably I find myself on here AGAIN with an issue. I'm finding I'm getting what I believe to be clutch slip especially in fifth gear under full throttle. This seems to have come about since sticking a superchips stage one tune on the car pinched from my brother. The clutch is new and has done about 10,000 miles of gentle driving and is a genuine 850r clutch from Volvo including pressure plate and release bearing. Flywheel was skimmed. Seemed to be fine on the stock tune and I seem to think it being okay initially on the stage one but now I'm getting nearly 500 rpm surges that are not correlated to speed under full throttle at about 70 mph which then drops back to where it should be. Initially I thought it may have been wheel spin related but pretty sure it's not now as surging is getting worse.

    I've got no sign of the rear main seal leaking or any oil contamination down there and the rms oil seal is new as the engine was rebuilt

    I've included a photo of the map graphs to show what it's apparently putting out as tuning is kind of new to me but I thought the 850 r clutch should be easily able to handle 250 hp or more. My brothers car seemed fine with it and if anything is less supporting modded than mine is

    Can anyone think of anything else it could be?

    Thanks

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    Last edited by Bigsi15; Monday 13th February 2017 at 07:22.

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    Two possible things I can think of, you're either way out with the torque figures due to your car being very different to the dyno'd car or you have worn out your clutch. A good 850R clutch will cope with 400Nm. I see it all the time with one customer able to do 20k with 500Nm and another only getting 5k with 400Nm, the clutches are consistent but unfortunatly the drivers are not.

    When fitting another ECU it's wise to at least check the fueling and knock. Knock is possibly the biggest cause of rod bending on 850s.

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    Thanks Tim, useful points again. I will try and get the car checked on that tune for knock etc, it does however seem to run very smoothly and nicely up until lately. I would like to think I'm reasonably gentle on the clutch I very rarely do aggressive pull aways, shift gently, no track use at all and only really the odd occasional hard pull onto a dual carriageway etc.
    I have done some ringing around trying to track down more information on this map and someone mentioned something about possibly a problem due to skimming the flywheel? I did have the face skimmed when I had apart to ensure it was flat and straight and it was done by a machine shop who specialise in engines but I wonder if it's possible They have taken just a bit too much off and so effectively simulated a worn disc??

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    Hmm maybe not the flywheel from what I have seen online as the whole face is flat on these cars aren't they so in theory lopping off say 0.5mm in the skim will just move the entire clutch including the disc and pressie plate 0.5mm nearer to the engine?? This shouldn't affect the clutch as the relationship between the pressure plate is the same from the flywheel and the disc just maybe now means further away from the release bearing which won't affect tension on the pressure plate? I don't think our flywheels have a raised section for the disc to bite onto and a recessed outer area for the pressure plate to bolt to looking at others online do they??

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    Mine was fully skimmed like this one

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    Skimming the complete face won't cause a problem. You more than likely make more torque between 2800-4000RPM than the graph and that will cause the slip then.

    Until you do some more investigation I would slacken off your actuator half a turn.

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    I think you may be onto something there Tim, it seems to slip if the boost build aggressively and quickly for example it seems to happen if you suddenly plant your foot hard down about 70 mph where as if you accelerate more steadily it doesn't seem to slip. That would be about in the rpm range you're talking of as well. Excellent idea about the wastegate too il give that a try too thanks
    I'm certainly not getting a strong smell of clutch after a bit of a spirited drive or after a long motorway stint so I'm hoping it's generally okay for the time being.

    Interestingly I have spoken to Sachs about the part number of the pressure plate and mine collaborates with a T5r. I don't know if there is any difference between the T5, T5r and then the r as for some reason in the back of my head I have that the T5 and T5r share the same clutch with the r being bigger/stronger. The disk is certainly a different size than the one that came out or is it just the smaller diameter disc that gives that tighter clamping pressure not the plate?

    Would running this tune in an engine with a slightly larger bore causing some increase in torque??

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    Ok so possible cause, slave cylinder...
    No leaks etc but Should I be able to push it in when the clutch pedal is fully up?? If I reach in and press the end of the piston in (towards the starter motor direction) I'm able to push it in maybe another centimetre Or just under and it feels slightly squidgy. Should I be able to do this? If it needs a bleed or something to allow it to fully retract then it might explain the slipping if it's not allowing the clutch to completely engage?

    Thanks
    Last edited by Bigsi15; Monday 13th February 2017 at 22:07.

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    You cannot push the slave cylinder. You can push the rod that's in line with the piston, you're over thinking things. Check the known problems first, if it boost higher when you stamp on the accelerator than building up from lower revs you may need a new TCV. You cannot get the old BCSs but the colours are the same so just remove one hose at a time.

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    Sorry yes that's what I was getting at just the piston arm, moves in very easily (can push with a finger). I'm Clutching at straws I think now tbh tim really don't want to have to open it all up especially with such low miles on it. Iv tried your earlier suggestion and wound the wastegate back 1 turn which has made it more gentle but still slips like before. Boost builds fairly gradually and doesn't overboost (sighs in despair)

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    Ok, with not knowing how much torque it was or is making it's not an informed decision but I think you will need a clutch.

    More importantly than fitting another clutch you need to know how or why this one failed or you will have the same problem again if you fit the same clutch.

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    Yeah completely agree, if I do have to go through the process of changing a clutch I certainly don't intend to do it a 3rd time! Very surprised and disappointed in this clutch if it is that which is the cause. In any case an r clutch should not fail in under 10k miles of road driving even on a stage 1 tune (unless like you say it's pushing out a ton more torque than we think but I find that unlikely given I have no other major upgrades ATM like turbo or exhaust).

    Think I will keep going on it and see how it goes for now and start saving for a better clutch. Maybe just a patch of contamination etc but unlikely. Gearbox rattles like mad too (see my other post) so probably do both when it gets stripped down. Yay money...

    Thanks as always for your help tim

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    Tim is it possible for slipping to occur due to a gearbox fault? Mine sounds so clunky I wonder if the dif is going or something?
    As it sounds so bad if I do open it all up to check the clutch I will probably replace that too.

    I believe there are 2 boxes of this era an m56 h and l without too much difference in ratio (not for me as a road or occasional track user at least), but will the boxes from the na cars fit as well?? I believe the diesel box has a different layout for the starter etc?? Also not 100% sure on which shaft sizes came from which year

    Any help again would be much appreciated thanks

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    Diesel 'box has a different bolt pattern Fella, so won't fit at all.

    What 'box are you running, standard fit M56?
    Any slip in there would be mangled gears, resulting in complete stationary-ness

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    You can fit any of the petrol S,V,C70 boxes, if I were removing the box AGAIN to change the clutch I would change to an internal slave cylinder box as the pedal is about half the weight and gives far better feedback. You would also need the pipe to the slave cylinder if you have an OBD2 socket or if OBD1 then also the pipe from the master cylinder.

    No the gearbox won't cause the clutch to slip in your case.

    I do clutch discs that allow up to 20% more torque with the same cover.

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    Thanks guys food for thought. I guess it doesn't matter what shaft diameter either so long as the clutch is to match?? Tim do your discs just fit with the 850 pressure plate?



    This is the noise I have as well. Shifts fine and never jumps out etc but sounds terrible especially when engaging gears. Perhaps just bad backlash but surely not normal?!

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    Are you turning the intermediate driveshaft back and forth there? (hard to tell, I'm on the phone)

    Sounds like a slack diff to me, would be fairly normal I would have thought if there's big mileage on the 'box?
    Still wouldn't cause any slip though, so unrelated there.

    If it was the diff, it would probably be most apparent when on and off the throttle.
    Would also sound worse to you in the car if you have poly mounts etc
    Last edited by Doingitsideways; Wednesday 15th February 2017 at 11:53.

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    The discs are a direct replacement for a standard Volvo ones.

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    Think I am turning the wheel although can't remember which side. It does the same noise whichever side I turn with a little delay before the other wheel turns. Does also do it like you say when quickly letting of and getting back on the throttle.
    Box hasn't had too many miles for these cars I guess at around 175k miles but still a few! Is it something to be too worried about or just worn and will make noise but go on ok?? Oil has been changed recently with volvo oil until it came out the top hole.
    It's a fair clunk if your rough shifting and about 10% of the time it may not do it at all. Also makes the noise if in neutral and engage then disengage the clutch quickly, sounds a bit like a knackered dual mass flywheel then. Shifts fine though.

    Thanks tim if they aren't scary money il be coming your way most likely if/when it gets done!

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    I'd live with it, but I'm sure someone more knowledgeable than me will be along shortly.

    Been a long while since I had a manual petrol.

    The gearbox could be about to explode on my diesel and I wouldn't hear anything over the engine
    It has done nearly 312k though, so maybe...

    Could be barking up the wrong tree, but I just remembered I had a similar noise on one of my XR3is.
    Turned out one of the driveshafts wasn't all the way home in the gearbox.
    Maybe worth a look, although can't remember if it would be possible for them to not be on these.


 

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