Clutch Judder and vibration.

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Shagrington
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Re: Clutch Judder and vibration.

Post by Shagrington »

Here is a theory that may be complete :censored: Is it possible the revs have dropped quite a bit between gears so, if they've managed to get below 4k, with the lack of low down torque it is just taking a while to get back towards the optimum where it will continue accelerating - the revs do tend to drop quite quickly in gear changes and this could be exaggerated further up a steep hill and could give a feeling of a sort of lag I'd guess?
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Re: Clutch Judder and vibration.

Post by Pioneer44 »

Thanks for the thoughts on the cause of the issue.

I`m not sure the lag is being caused by the revs dropping below 4k as the 1st to 2nd gear change uphill requires a fast change and as I hit the redline in 1st it only drops to 6k ish as 2nd is selected, although I appreciate the 8`s engine lacks low end torque..

As the weather is looking dry and bright this week I`ll try the same uphill change with the DSC/TC completely switched off to confirm it`s not the TC momentarily kicking in.

The Exedy clutch fitted isn`t a competition/racing clutch as far as I remember and simply the standard, recommended one for the 8 and although the Blueprint ones are generally regarded as not up to the job it certainly had a smoother more progressive engagement and was easier to rev match on downshifts than the Exedy.

I`m fairly confident the gearbox/Syncromesh/driveshafts/UJ`s are all good as there are no knocking or whining noises which only really leaves the clutch cover/plate & bearing or possibly the slave or master cylinder to be the culprit or even the spring on the clutch fork ? But I will try the DSC/TC switched off and report the findings.
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Re: Clutch Judder and vibration.

Post by Lemon »

what tyres are on the car, RX8's do like to throw the traction control in very early if it thinks you are going to slip.
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Re: Clutch Judder and vibration.

Post by Pioneer44 »

The rear tyres are Dunlop Sport Maxx with around 3-4mm each side.
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Re: Clutch Judder and vibration.

Post by qwakers »

your symptoms cannot possibly be clutch related. a clutch either slips or it doesnt.
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Re: Clutch Judder and vibration.

Post by warpc0il »

Pioneer44 wrote:
Mon Jan 20, 2020 12:16 pm
The rear tyres are Dunlop Sport Maxx with around 3-4mm each side.
What sizes and what are the front tyres?

The systems determine wheel slip/spin/lock by any differences in the rotation of all four wheels.

It only takes a 1% difference in effective tyre diameter to prematurely trigger the TCS/DSC or negate the benefit of ABS/EBD
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Re: Clutch Judder and vibration.

Post by Pioneer44 »

Front tyres are Maxxis Pro with 4-5mm each side, all tyres are 225/45/ZR18.

To dismiss the problem as not possibly being the clutch at fault "as they either slip or they don`t" seems a little too simple. Maybe the fingers on the cover are weak or were bent/damaged upon installation (which would cause the slight roughness at the bite point) and the increased load at full throttle uphill is showing this ?

In hindsight (a wonderful thing) it would have been better if I had fitted the Exedy clutch, having changed several rwd car clutches when I was younger, at least then it would have been done with care. Surely the 8`s clutch change isn`t beyond a competent DIY`er with the correct tools etc ?

But as previously mentioned I`ll switch the DCS/TC completely off and attempt the uphill test when time allows and report back.
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Re: Clutch Judder and vibration.

Post by Pioneer44 »

Follow up.

Took the car out yesterday and tried the same 1st to 2nd gear uphill acceleration without DSC/TC. The problem is exactly the same.

Then asked a friend to drive it and he is of the same opinion that the clutch is beginning to fail, although it doesn`t slip when testing it by trying to set off in 4th or 5th whereby the car stalls immediately the clutch pedal is released. He also agrees the pedal engagement feels lumpy and isn`t nice to use.

I thought that by fitting an Exedy clutch there would have been no more problems so either the clutch supplied is a fake or more likely the cover fingers were damaged upon installation. There is now also the return of juddering when in reverse, so I`m right back where I started 9 months ago albeit £600 out of pocket.

Can anyone recommend a competent, trustworthy technician around North Derbyshire to fit another clutch ?

I`ve contacted Exedy UK who say they will replace the clutch if found to be faulty, but as they claim to have never had a problem with their RX8 clutches I`m inclined to believe it was damaged by the gearbox input shaft hitting the cover fingers when installing, so a full refund is highly unlikely ( plus the high cost of couriering such a heavy item is prohibitive).

I`ll post again once the clutch has been removed, meanwhile I`ll recommision my 328ci (which is an auto) !
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Re: Clutch Judder and vibration.

Post by Ainmhidh »

Depending where you are around north Derbyshire, you could try Motorsport and Performance in Bately, about an hour north of Chesterfield as the nearest rotary specialist I can think of. If it's clutch then it probably isn't necessary to use a rotary specialist, but if it's something else, they'd hopefully be able to give you a clue.
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