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MG MGB Technical - clutch problem

posted this on the general MGB by mistake. This is where I want it.

I have a 74 GT. Suddenly it will not shift; gears grind, it will not even go into reverse. There is still a lot of travel at the slave cylinder, as much or more than in my 77 roadster. Can anyone think of anything that could be wrong EXCEPT that the clutch is shot? Please tell me I don't have to pull that engine!!
Chuck Horsley

Make sure you check both postings for replys.

What exactly do you mean by "There is still a lot of travel at the slave cylinder"? Travel still remaining (as in it barely moves), or it travels a lot?
Steve S.

I think Steve is trying to find out if the slave is moving fully out with the pedal.
I had a Saab once with the same symptoms. The rubber hose between the slave and the body had split internally (all the fluid went into expanding the hose slightly.) a new hose cured the problem- took a while to figure it out though.

If you pump the pedal up and down like fury a dozen times, does the clutch work immediately you stop?
That would indicate faulty seals. If there is no fluid loss, in the master cylinder. Otherwise, a fuid loss is easy to spot, as it comes out of the rubber cap.
Martin Layton

The travel at the slave cylinder means you will have to pull it. See the other posting I did, but in short, if you have tranny problems, get an overdrive transmission. Don't pour money into the regular 4 speed.
Richard Morris

If the slave push-rod is moving its normal amount back and fore i.e. about 1/2" to 5/8" then the problem is inside the bell-housing. If much less than that then probably a hydraulic problem i.e. much easier to resolve. It is only the clutch cover diaphragm springs that push the slave piston back into its cylinder and the fluid back into the master. If there is anything wrong with the release arm or release bearing so that thge slave push-rod is not eventually releasing th3e pressure on the driven plate, there will be no return pressure to push the piston back into its cylinder, and successive pumps will push the slave piston right out of its cylinder and dump fluid on the floor. Only a couple of pumps is needed, BT, DT.
Paul Hunt 2

Dave DuBois's posting is very relevant as it is important to determine whether or not the clutch disc has rusted to the flywheel. Failing that it seems that the problem is in the clutch cover and this of course means an engine removal to replace the three part clutch kit.
Iain MacKintosh

Good point about the clutch disc rusting to the flywheel, although I did take it that this was a sudden change given the wording of the original post and not resurrection of a long-term parkee.
Paul Hunt 2

Yes, so did I and for that reason it seems that the diaphragm spring in the clutch cover may have partially collapsed necessitating replacement of the cover.
Iain MacKintosh

But wouldn't a collaped spring *remove* pressure from the friction plate? And make non-disengagement i.e. grinding even less likely? And make *slipping* under load more likely to be the problem?
Paul Hunt 2

Slipping under load can be more common with a partially collapsed diaphragm spring but if it is partially collapsed i.e part of the diameter of the spring not operating you can then also have the situation where it does not pull back either, so grating becomes more of an issue as well
Iain MacKintosh

Yes, I can see that. Whatever, if he is getting the 1/2" to 5/8" of travel of the slave push-rod then it is an engine out jobbie in any event.
Paul Hunt 2

Here is an OD transmission,1

Or have you already fixed it?
Richard Morris

When the diaphram spring breaks it causes the pressure plate to be pulled back on one side only which makes the clutch still feel almost normal, but one side drags behind holding the clutch disc in contact with the flywheel causing an amount of drive and therefore grating of gears. Its not uncommon.

This thread was discussed between 07/01/2007 and 14/01/2007

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