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Re: Clutch shudder

Subject: Re: Clutch shudder
From: Barney Gaylord <>
Date: Wed, 11 Sep 2002 13:05:26 -0500
At 01:05 AM 9/11/02 -0400, wrote:
>.... '69 MGB/GT.  Before car is up to normal operating temp, it will 
>sometimes violently shake when I release the clutch pedal in 1st 
>gear.  What exactly is causing this clutch shudder?

Could any of a number of things.  If you happen to live a good life, and 
you get really REALLY lucky, maybe it's just bad engine mounts.  But I 
doubt it.

My first suspect would be a worn spigot bushing in the tail end of the 
crankshaft allowing the gearbox input shaft and clutch disk to wobble about 
off center.  Cure would be replacement of the spiggot bushing.  Loose 
splines in the clutch disk (or on the input shaft) can aggrevate this 
situation.  A glazed surface on the clutch disk can sometimes do it.  For 
either case the cure would be replacement of the clutch disk.  A much less 
likely but possible item would be a carburized surface on the flywheel or 
pressure plate cause by repeated exposure to high temperatures (slipping 
clutch, high torque engine, leaded left foot).  Cure for this is to reface 
the flywheel and/or replace the pressure plate.

While any one of these things could be causing the problem, it is much more 
likely a combination of more than one item.  The good news is that fixing 
just one of the ailments is likely to stop the shaking.  The bad news is 
that you have to part the engine from the gearbox to fix any of them.

>   Will I cause harm by continuing to drive in this condition?

Well, probably not immediately.  But being bad enough for long enough, 
severe shaking is bound to eventually cause some problem in the 
drivetrain.  This might be wear on the clutch splines, strange failure mode 
for the clutch release bearing or the release arm, broken gear teeth in the 
transmission or differential,  worn thrust washers in the differential, 
failed u-joints in the propshaft, damage to various ball bearings.  Failed 
engine mounts may lead to cascading damage to engine accessories, radiator, 
hoses, linkages, exhaust pipe, exhaust hangers.  And then the remote 
possibility that your life may be on the line if something serious breaks 
while traveling at speed.

This is definitely not good behavior for an MG.  It isn't just 
irritating.  It has the potential to become a serioius inconvenience and 
expense.  In other words, you really ought to fix it pretty soon.

Barney Gaylord
1958 MGA with an atittude

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