Clutch slip

[Tony Griffiths]

So, to be clear, do you mean the slip takes place on a straight action of hill AFTER you have turned a sharp corner onto it? If so, is it instantaneous or does it last a while?

Correct. Turn right - or left - on a flat section of road and drive up a straight hill. After some indeterminate point that various inconsistently, the clutch will sometimes slip, then grip again - or force a stop. After which, it does not slip again. As we are not short of hills in the Peak District, I've just returned from a test drive. On our "normal" hills, 1 in 8 to 1 in 12, it proves no problems at all; approach in top, down to second, occasionally and it pulls with without slipping.
Let's try something steeper - the 1 in 5 Cressborok hill. After a flat-out run through the left-hand turn on approach, slip stated in second gear about one-third of the way up. Dropping down to 1st and nursing it, it picked up; a change into second and, with full throttle, slip again; backing off, it grips, down into first and in climbs slowly up to the top without slip. Back to the bottom for a second run, but this time from a standing start. No slip at all in first so, flat out, peak revs and into second - and it pulls strongly without slip until down to a crawl on the steepest section; into first, full throttle and - surprisingly - again no slip. Change up into second - still no slip until, just before the top, first is needed for the last few yards, but still no slip. Conclusion? Might the condition be just "in extremis" - maximum power and a maximum gradient? I suppose the next trick will be to put some weight into the car and see what happens....

[Alan]

Slacken the dampers right off and see what happens.

[Mark McKibbin]

It sounds like clutch slip to me, usually it shows itself in top gear. Have you just lubricated (excessively) the throw out bearing? is the gearbox overfilled?

[Tony Griffiths]

It sounds like clutch slip to me, usually it shows itself in top gear.  Have you just lubricated (excessively) the throw out bearing? is the gearbox overfilled?

No lubrication of the thrust bearing - and the gearbox oil level has been lowered from the standard. Oddly, it never slips in top gear; one can get down to crankshaft-breaking speeds in that gear on a hill - and, nothing.

[Alan]

I live in Cheshire and we don’t have hills or I’d see if mine did it. I admit I’m going off the idea of wheelspin, and tending towards the clutch. The release bearing is returning properly isn’t it? And not maybe sticking.

[Steve Jones]

I've had something similar, sort of, on my trials car. When setting off at the start of a section the clutch will slip but eventually bite then all OK. Eventually I realised that the release bearing was binding, slightly, on the gearbox nose. In my case no doubt a product of years of trialling, mud and muck and misuse causing wear between the two. Lubrication through the bearing lubricater and working the clutch at the same time solves it and such lubrication has been a pre-event essential for some years.

Steve

[James Anderson]

Just add to the mix, my GE Cup does the same sort of thing on hills in top but when I change down, it is fine (only slower!). I think this definitely clutch slip but why should it be fine in lower gears?

[andrew34ruby]

Just add to the mix, my GE Cup does the same sort of thing on hills in top but when I change down, it is fine (only slower!). I think this definitely clutch slip but why should it be fine in lower gears?

The torque to make the clutch slip is always less in lower gears. Torque multiplied by revs equals power. so in lower gears you get the power to push the car along with less torque and more revs. Higher gear means less revs, so needs more torque to push the car along. More torque makes the clutch slip.

[Tony Griffiths]

I've had something similar, sort of, on my trials car. When setting off at the start of a section the clutch will slip but eventually bite then all OK. Eventually I realised that the release bearing was binding, slightly, on the gearbox nose. In my case no doubt a product of years of trialling, mud and muck and misuse causing wear between the two. Lubrication through the bearing lubricater and working the clutch at the same time solves it and such lubrication has been a pre-event essential for some years.

Steve

Thank you; I'll investigate and see if that makes a difference.

[James Anderson]

Thanks for that explanation, just hoping not to have to take the engine out again! I might try an endoscope to see hope thick the linings are and that might indicate too much oil/maladjusted clutch pedal or binding clutch release bearing.