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MG MGB Technical - Slipping clutch

Before I extract the motor/gearbox from my '70 GT, I feel compelled to ask this question. Are there other issues to consider that would cause a clutch to slip? There's relatively low mileage (26,000 miles) and the slipping seems more pronounced once the car is well warmed up. master cylinder functions OK. Slipping is noticed with aggressive acceleration. I plan to replace the 4 speed with an OD unit. Also, any advice on replacing seals, gaskets, rubber mounts, etc. while the unit is out is welcomed.
Thanks
Tim
Tim

Check that there is some play in the rod from the clutch pedal into the master cylinder. If it is tight the master does not come back far enough to open the bleed hole when the pedal is up. As the fluid gets hot and can't escape back into the master it can put pressure on the clutch arm.
John H

There won't be any free-play as such as the spring in the slave cylinder keeps the linkage pressed together, but you should be able to push the slave piston further into its cylinder and *create* free play. Just be aware that when you do that you could push some fluid out of the top of the master so protect against spillage, and after doing so the clutch biting point will be lower than normal. But as John says you must be able to create some free play, or fluid expansion will cause clutch slip and wear. You should be able to get 100k miles out of a clutch, it does depend on driving style and technique, but that is very low mileage for a worn-out clutch.
Paul Hunt 2

The PO was a "little old lady" who drove the car to the country club and back, somewhere in British Columbia, which can be hilly, if not mountainous. Never met her (bought car thru estate sale)so I'm unaware of her driving style. But the clutch has slipped since I've owned it, in varying degrees. I'll check out the linkage. Thanks all for the info.
Tim

Fluid leak onto clutch plate?
Dan Robinson

That usually causes a grabbing clutch, not a slipping, paradoxically.
Paul Hunt 2

If I let the clutch out slowly, without giving it some gas, it "chatters" somewhat. Normal clutching, it doesn't. Not sure what that means.
tim

Tim the most common cause of a slipping clutch at low mileage is a cracked diaphragm spring in the pressure plate.
DENIS4

Tim - if you aren't giving the engine any throttle and expecting the car to move then it is probably the engine struggling to keep going under the load and shuddering at the very low revs.

But if you get a vibration and the gear lever wobbles about while maintaining at least idle revs as you let the clutch out, that is probably judder, which is a completely different thing to slip. Slip is when the clutch is fully engaged and you aren't riding the pedal, you increase the throttle opening, and the engine revs go up without any corresponding increase in road speed, a bit like an automatic. This is noticeable in 4th or OD 4th first, then progressively in lower gears as the slip gets worse.

No clutches should do it really, but some do. My roadster does it at low revs, so I just manouvere with slightly higher revs which controls it. Other will tell you their car judders if they slip the clutch with *higher* revs. Learn what your car prefers, then do it that way.
Paul Hunt 2

Tim,
If the PO slipped the clutch getting underway, the pressure plate spring(s) may have lost their tension. Replacement is the only fix.
Lee Bradley

Lee, that's what I suspect. The motor comes out at first snow, which here in the most southern city in Canada, could be in January.
Tim

The life of a clutch is directly proportional to the skill of the driver.
John H

This thread was discussed between 18/10/2007 and 26/10/2007

MG MGB Technical index

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