Jaguar 340 Clutch Release Bearing

Hello every body,

As a new member of this forum, I can not post more than 3 posts in a same topic, so I start a new one ! The topic that I’m talking about was titled “Clutch Fork Travel” (49/49 posts).

I now know the reason why it was a hell to engage any gears on my 340 !!

This release bearing only did 100 kilometers ! How explain that ? Bad quality part or bad fitting ?



Job to say by a picture , if you removed it , you would know if it was a bad fit !
To look like that after what 60 miles , I would say Bad quality , looks like it has just broken up .
First time I have seen one like that !

pleased to greet julian. several versions of throw out bearing will fit. but not work as you should have synchromesh first gear unlike 3.4 l earlier. your brg from photo looks reasonable but abused, shattered face & spalled inner bore? real Borg and Beck or AP versions still available cheap from jobbers or online sites. john

As I am preparing for an engine overhaul and clutch replacement I would be most interested to know who the maker of this bearing was. The damage is clearly not normal wear. Given the huge number of hours changing these incurs, it is imperative a quality durable one is fitted. My shop has had some bad experiences with Borg & Beck clutch covers on Austin Healey 3000s so I he is skeptical on their current quality although release bearings are a different animal.

As a professional, I purchase all my Jaguar and Daimler parts to SNG BARRATT. I will ask them who is their supplier for this clutch release bearing, and then let you know…

Thanks for your replies

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Hi John - it’s funny that you mention the issues with new Borg & Beck clutch covers. I had an issue over the past summer with a brand new Borg & Beck 10" Clutch Cover that I was installing in a '61 3.8 Mk2. This is obviously the 3 lever-arm style - not diaphragm - purchased from SNGB. I’ll say at the onset that SNGB took care of the problem immediately but it is possible that the problem I encountered could explain that odd damage to the OP’s throwout bearing.

I received the clutch cover undamaged and sealed in it’s original packaging. On initial inspection it looked perfectly fine but after installing it and the brand new clutch disc on the flywheel (so everything was now under tension) I noticed something odd - The release surface that the throwout rides on was not parallel to the flywheel after snugging the whole thing up. Obvious in this pic:

The issue was because the three arms that operate the pressure plate were not adjusted correctly at the factory. I immediately exchanged it and the replacement was fine but had I not noticed this or it was less obvious because they were less out of adjustment, it might explain the strange damage to @Allister_Mills throwout bearing. I imagine that a throwout surface that was not parallel could give the throwout bearing a bit of a beating every time it was operated… Certainly a theory about what could have happened to the OP’s car.

Also definitely something to look at for anyone installing a new, lever-style clutch cover


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In talking yesterday with the owner of my shop he tells me from prior relatively recent experience he is now having a trusted shop here locally rebuilt the clutch cover that will come out of my car. He has had too many issues with clutches in big Healeys. Given the huge amount of labor in changing one in a 3,8S I am keeping my fingers crossed that this is a satisfactory solution. I believe my full synchro 1965 3.8S has a spring type like shown in your photo not diaphragm type that was used later.

yup some bad experiences reported with new clutches, both by professional shops and individuals (like me). and XK specialist here in the uk recently reported they had to change 3 in cars they had prepared for customers due to faulty manufacturing. I spoke to Rob Beere and he advised that AP and Borge and Beck had moved their manufacturing to a new facility in Italy and were experiencing issues with the exchange of skills/procedures etc etc.
my problem was with a AP diaphragm clutch I changed it for a Borge and beck and all is well on the MK 2

Just for my info: Are all Borg & Beck the spring type and AP the diaphragm type? Was there a change over with the Mark II and 3.8S/3.4S cars at some point?

No. BB make a diaphragm clutch also.
The change over was in 1964 when the all synchro box was introduced to the mk2. I believe the Stype and etype had these boxes and clutches a year earlier.

With best regards

The diaphragm clutch release bearing has a thicker carbon because the diaphragm cover is thinner so if you have the old style clutch it could have been rubbing constantly and overheated.


My 3.8S was made in early November 1964 and is 105 VINs from when they went to the full syncho gearbox but I am not sure which clutch it has currently, been decades since it was last changed.

I do wonder if the root problem here was caused by the release bearing being in fairly hard contact with the clutch mechanism continually. In other words it had no clearance when the clutch was engaged, thus leading to overheating and subsequent failure. It would also explain why it was so hard to engage gears.

Last year I fitted a diaphragm clutch to my Mk2, changing from a spring style. The release lever sat almost at the rear of the rectangular cut out on the bell housing and gave me some concern that there was enough rearward travel to release the clutch. In fact there was since only a small movement is necessary to do the job. As the clutch wears, the lever position moves progressively forward and the use of a long cylinder accommodates this.

Clutch Lever Position

The original slave cylinder was a short style that means you must adjust the pushrod to get a running clearance. This I found difficult to do and so changed to the long style cylinder that takes care of the clearance automatically and compensates for any wear.
I assume it does actually run with a light running contact.
2000 miles later it still seems OK.


I believe there should always be a small amount of clearance between the carbon release bearing and its wearing surface on the clutch cover. On my car there is a coil spring that causes full retraction of the slave cylinder to create this clearance. The slave in your photo does not show this spring. Is that the way it is supposed to be?

My first car was a 948cc Bug Eye. I learned the hard way not to sit at a stop light with the clutch depressed with the graphite throw-out bearing grinding away. Not so with american cars.
Pat H

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Well yes this is what I used to think too and you are right for the coil spring clutch use. But the later diaphragm clutch system is actually quite clever and does not use a spring.

The short slave cylinder e.g C21470 uses a return spring so that the slave piston bottoms in the bore when the clutch pedal is released. Under this condition you do indeed adjust the push rod to achieve a slight clearance at the throw out bearing.

But with a long slave cylinder e.g. C24145 the piston takes a position well away from the bottom of the cylinder bore and so a spring return would cause great free play at the thrust bearing. I think that the head of fluid in the hydraulic circuit is sufficient to apply just enough force on the operating rod to keep it in contact with the operating fork and thus light contact at the throw-out bearing face. This design means that you do not need to adjust the operating rod length as the clutch wears whereas with the short cylinder, as the clutch wears the clearance is taken up and requires a reset.

The rule seems to be that with a spring clutch you use a short slave cylinder plus spring. The diaphragm clutch is used with a long slave and no spring.

Refer also to the bottom of page 116 of the Mark 2 parts manual.

Tricky eh?


Bruce, If I can trouble you for a few more questions. After you converted from a spring clutch to a diaphragm one did you notice a lighter pedal motion? Can you supply me some measurements of the slave so I can compare what is on my car in the event the wrong one has been fitted in the past. My 3.8S (full syncho gearbox car) does have the retracting spring but that may be fitted in error for all I know. Thanks for your efforts.


Yes the pedal effort is definitely lighter with the diaphragm clutch.
My car is in winter storage and not accessible to me now to make a measurement.
I would simply say that if you have a spring fitted, then you probably have a short style slave cylinder. The long cylinder could be fitted I suppose, but if so it would be operating by resting at the bottom of the bore.


I just had a brand new TOB fail in my E-Type within 25 miles after installation. It came with a new B&B clutch kit for my new 5-speed gearbox. We (garage mech and I) looked at another brand new TOB that was available from the same supplier in California, and it too was faulty. A brand new TOB was ordered from Denis Welch, and so far (knock on wood), it is working just fine. Note: Original bearing on left; failed bearing in center; brand new bearing with chip and cracks on right in photo.

I would have invented new bad words.

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