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MG MGB Technical - clutch moves car does not

Dad and I put a new B & B clutch, etc. in about 5 months ago. Lately, I had trouble getting into all gears without grinding. The pedal seemed to vibrate when not pushed in. I thought to check my two clutch cylinders, but now, I put my 75B in gear and it does not move. Just before no movement, while in first gear the engine would rev up but car barely moved. Now no movement. All clevis pins are in; the pushrod from the clutch slave moves about 3/8 or 1/2 inch. Seems to be normal movement. Clutch resevoir is full. I do not see fluid leaks. The drive shaft is ok. I do not know about transmissions or am I back into a clutch problem? I have a big date next weekend, please help. There is no MG mechanic in this small town.
brian beedie

If the problem was clutch hydraulics, you would
have problems disengaging the clutch, but the
car would move when in gear. If the problem was
in the transmission, I would think the layshaft
or mainshaft would have to break completely to
duplicate your problem. i.e. one or two gears
might fail, but not all at once.

Based on the symptoms of vibrating clutch pedal
and no movement of the car, I would guess your
clutch cover is broken (i.e. broken springs) so
insufficient
pressure on the disk, and no motion transmitted.

Let's see what others have to say -- there may be
some more tests you can run before pulling the engine.
Ronald

Hi,
Is your foot off the pedal when it Vibrates? If not and you are depressing the pedal and it vibrates and the car wont move when released you have broken springs in the pressure plate. Shut down the engine put it in gear and let out the clutch pedal. Turn the key and see if the cars moves if so then the release bearing is defective and wont let the clutch fully engage with the engine running. If the car don't move then it's the clutch. God forbid i hope your tranny input shaft is not broken.

cec
Cec Fry

Brian,
Had this problem on my race B once. The lining had come off one side of the clutch disc and lodged between the flywheel and presure plate so the pressure plate could not move far enough to reach the disc.
You might as well pull the engine and transmission as whatever is wrong will probably require going in anyway.
Leland Bradley

I had a similar problem years ago in an MGB-GT, but with mine there was no vibration - I just lost all forward movement while in the fast lane on the lower deck of the Bay Bridge, San Francisco to Oakland. The shift lever would move easily into all gears with the clutch pedal depressed, but the engine would simply rev with no action at the wheels.

Towed it home and found that the rebuilt clutch disc had sheared in two at the metal web between the spring hub and the outer ring of friction material. I now have that ring hanging on my garage wall with the admonition "NO REBUILT CLUTCH DISCS" written in the center to remind me!

Cheers,
Paul Kile
Paul Kile

If the slave piston is moving 1/2" or so with the pedal, and more importantly moving back again when the pedal is released, the hydraulics are OK and so is the mechanical linkage to the diaphragm spring in the cover plate. There is some other mechanical problem, e.g. Paul's non-clutching clutch plate.
Paul Hunt

Put the car up on jackstands and make sure it is secure. Start the engine and engage first gear. Very carefully, crawl under the car and look to see if the prop shaft is spinning. If it is spinning, the problem is a broken half shaft--rather rare with a B. If it is not spinning, it is a problem forward of the prop shaft--clutch, pressure plate or tranny. Les
Les Bengtson

Les,
Thanks for the heads up. I have had a couple of 'B's quit moving when the spider gear/shaft broke. Although Brian should not have to jack it up to check. Just put it in gear and check the speedometer.

Leland Bradley

Thanks to you all. Brian and I tried once more to go through all your suggestions. The throwout fork arm moves both directions about 1/2 inch. We bled the slave a few times to see if the flex hose had flakes in it (Brit-Tek advice). The drive shaft does not turn. We did achieve a small forward movement in first gear but it took way too many rpms. I think we have to pull the engine and look at the clutch mechanical system. Thanks for the help.
Brian Beedie

Leyland. No matter how long you have been doing this, you learn something every day. (At least every worthwhile day.) Thanks, "I never thought o' that". Les
Les Bengtson

This thread was discussed between 10/03/2002 and 13/03/2002

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