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MG MGB Technical - Slipping Clutch

Happy Friday all,

I think my clutch is slipping..

When driving my '78 BGT, if I apply hard acceleration sometimes the rev's shoot up but I don't get any drive. If I ease off then the car picks up and it's okay.

The clutch has done around 63k.

Does this sound like a classic case of clutch slip or something else?

If the clutch is slipping what can I do about it. I know that I can install a new 3 piece clutch but can it be restored or repaired or is there anything else I can try to remedy the problem?

Cheers,

JE
J Elliott

Yep. It sounds like your clutch is worn out. Sixty three thousand miles is a pretty good life for a clutch.

I don't think that there is anything that can be done, other than to replace the clutch. The springs on the pressure plate automatically adjust for the wear of the driven plate. The hydraulic clutch cylinder automatically adjusts for wear in the throwout bearing.

Don't wait too long to have it done. The driven plate is constructed much like a brake shoe or rotor; there is a friction compound that is rivetted onto the steel disc. If the compound wears down too far, it can expose the rivet heads, which will score the flywheel.

The flywheel can be removed and turned on a lathe, just like a brake drum or rotor. There is a limit to how many times this can be done, before the flywheel becomes unuseable.

While the engine and transmission are out, consider having the rear main oil seal and the front transmission oil seal replaced. The parts are inexpensive and you will already be paying for the labor to remove the engine.
Paul Noble

Paul,

Paying for labour..not me! :)

Isn't that what this list's for?

(Just one more thing to add to my list of things to learn and then do to the MG this summer)

Thanks for the advice about the seals..


James
J Elliott

I thought about adding "(or doing it yourself)" at that point in my reponse, but I thought that I was being too wordy is it was.

When I did mine this past summer, I did the following "might as wells":

replaced rear main oil seal

replaced front transmission seal

replaced side transmission gasket

replaced oil pan gasket

replaced exhaust doughnut gaskets (they seldom survive having the exhaust disconnected)

cleaned and painted the engine

replaced the spigot bushing

replaced the throwout fork bushing

replaced the clutch slave cylinder gator

replaced the clutch slave cylinder pushrod (the hole was worn badly oval-shaped) and the clevis pin

replaced the metal shims under the transmission front cover

cleaned and repainted the radiator and support

In addition, I would consider changing the clutch hose, examine the engine mounts and replace if necessary, examine transmission mounts and replace if necessary, engine tappet cover gaskets.

When you have the clutch off, examine the flywheel surface. If it is worn or scored, take it to a machine shop for resurfacing.

I would look at the propshaft u-joints. You have to disconnect one end, and you're under there anyway. Why not take it completely off and renew the joints. The parts aren't expensive, and it should only take an hour or so. I didn't do mine, because they had been done recently.
Paul Noble

To be absolutely sure it should slip most in OD 4th and least in 1st, whereas if it is the OD that is slipping it would be the other way round.

Don't be talked into using a roller-bearing release bearing instead of the standard carbon item, they are waste of money.
Paul Hunt

Nice list Paul N. but--I'd have to add Ring gear inspection at least and quite possibly [7 out of 10] replacement. As an aside replace the starter pinion whenever you replace the ringgear.
RIC
Ric

Interesting comment about the ring-gear. In 36 years of messing around with old cars, I've never replaced one. The only car where I definitely should have done was a 1961 Ford Anglia which had the old-fashioned Bendix starter drive. On most MGBs with the pre-engaged starter it's not an issue in my experience. But then I've never replaced a spigot bush either...
Mike
Mike Howlett

Jim. You can replace the clutch and do all the other things mentioned in 2 days or less. My wife and I did all Paul's items in 2 long days without any problens. Do It.
John
John Simmers

Okay, I'm going to do it and the other things Paul mentioned,

My shopping list has trebled now..I hope I can pick up some bargains at Stoneleigh!!

I'm pretty sure that it isn't the OD because I got it to slip in 4th non-OD and 2nd. It's only just started going so I'm going to drive it a bit until the tax runs out at the end of the month and garage it until I've got time over the summer to do it up.

John, I'll let you know if your time estimate is right!

By the way, as it's not going to be moved for a few months should I do anything to stop it seizing up? I'm going to put it on axle stands but is there anything else I can do?

Also, regarding axle stands, is it safe to work under/on a car that is only resting on axle stands?

Cheers all,

James
J Elliott

James: use good axle stands on solid footing. Make sure the car is level and secure, and be careful. Then it is safe.
John
John Simmers

James,
Before getting under the car when it's up on stands, try giving the car a gentle shove from several different directions. Grab on to it and try rocking it; you don't want the car rocking at all, say if a stand isn't seated properly to the ground. The car should be rock solid before you get under, then it's safe.

Best, Joe
Joe Ullman

Thanks John and Joe,

It's good to know these things!!

Regards,

James
J Elliott

...and drive the car as little as possible with the clutch slipping. Not only do you risk flywheel damage, but the thing could suddenly get to the point where it slips all the time. You might not get home some day.
R. L Carleen

Yes, my list includes a lot of items, but aside from the clutch kit itself, none of them are very expensive. When I did mine, I think that the parts total was only about $160, or which $100 was for the clutch kit.

As for the ring gear, I did inspect mine when it was out. I quess I forgot to mention that. There was no sign of worn or damaged teeth on either the ring gear or the starter pinion, so I left it alone. I do agree, though, that if your ring gear does need to be replaced, the starter gear should probably be done as well. If one is worn, the other will be too, and a worn gear will tear up a new gear in short order.
Paul Noble

Sorry for being ignorant, but why would a slipping clutch cause the flywheel damage?

James
J Elliott

Heat and scoring?
Paul Hunt

This thread was discussed between 17/01/2003 and 22/01/2003

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