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MG MG Y Type - clutch shaft bush?

Dear all, while poking around under my YT I noticed that there is a very "loose fit" where the clutch shaft passes through the bell housing. I have a 5/8" shaft and it almost seems it should be 3/4"? Also, the side not connected to the clutch has no circlip or anything to keep the shaft from moving side to side about 3/8 of an inch. Is this correct? As always, thanks in advance.

If any of this type of info is available on the web please enlighten me to its location. Tom
Thomas McNamara

The YT ended production in 1950, but the bellhousing which had the 3/4" shaft for the 8" clutch was not introduced until 1951, with the engine code changed to XPAG/SC2.
Thus if your car has it's original gearbox and bellhousing, and the engine having a 7.25" clutch, the shaft diameter should be 5/8". It is possible that the bushes are worn; also the shaft should have a circlip in a groove at the 'other' end.
However, as the shafts were in different positions in the bellhousing, you can check which shaft you should have. You should measure horizontally from the engine/bellhousing interface to the centre line of the hole which holds the oilite bush and shaft. If the distance is 62mm, the shaft should be 5/8". If the distance is 69mm, the shaft should be 3/4".
R A WILSON

thank you Mr. Wilson! After your comments I looked for the groove for the "clip" and sure enough, there it is under some heavy oil/dirt. Progress! Tom
Thomas McNamara

Perhaps should have said, when the 8" clutch was introduced, there were several changes to the bellhousing. Increasing the diameter of the shaft to 3/4" and moving it's position backwards by 7mm were the two most significant.
R A WILSON

The shaft could also be worn, particularly the side with the operating arm.
R A WILSON

I have a YB fitted with a YA engine which has the 7 1/4 in flywheel and clutch - however I have the later bell housing with the 3/4 shaft. This makes it difficult to set up the clutch release bearing and pedal as its out of alignment apparently. I really need to fit the 8in clutch and flywheel to sort it out. The clutch works but its not quite right. Any comments?
Mind you I have lived with this arrangement for years....
D MULLEN

Dave, I could source a YA bellhousing for you ?

Tony
A L SLATTERY

For D Mullen - not the best combination. As the 3/4" shaft bellhousing has it's shaft moved back 7mm, the carbon thrust bearing must swing forward more to release your 7.25" clutch. Unfortunately, it will also swing downwards, so the actual carbon ring will not be concentric with the clutch thrust ring, which will not receive a uniform force all the way round. In addition, the inside of the thrust bearing could touch the top of the first motion shaft, and extra force to release the clutch could break the 'fingers' on the operating arm that holds the thrust bearing. Your system might even work better as the clutch wears, as the clutch thrust ring will move backwards.
Either the YA bellhousing (gearbox and bellhousing out), or an 8" clutch and flywheel (engine out, crank removal ?), but winter is approaching.
R A WILSON

Further;
----- uniform force all the way round. More force will be below the horizontal centre line, so even though the flywheel and clutch are rotating, the lower section of the clutch will release, but the upper section might still grip slightly. I have seen similar happen on an older clutch, where the clutch thrust ring was not properly centralised. As I mentioned, the operation might be better when the clutch wears.
R A WILSON

Thanks for the offer of a YA bell housing Tony. Might be costly shipping from Aus. Sadly my daughter no longer lives in Melbourne having moved to Seattle otherwise I might have packed it in my luggage on a trip over...not that customs would have been pleased!
Will have a think about what to do and see what is available over here = quite why I never sorted it years ago is a mystery even to me. I believe Neil cairns YB has a similar arrangement as mine.
D MULLEN

I didn't actually say before, but the 8" clutch is not only larger in diameter, but also deeper than the 7.25" clutch, which is why the 3/4" shaft was moved back 7mm. The problems being experienced would be similar to those that arise if the friction, or clutch, face of a flywheel is machined back, rather than the rear (closest to the engine), when lightening a flywheel, so do not buy a flywheel that has been lightened on it's friction face. Grinding a few thou' off to remove scratches might be acceptable, but I would prefer to have that done myself.
(I have found shipping, rather than airfreight, from Australia not so expensive, and takes 2 to 3 months).
R A WILSON

I am posting on this thread because of the info on it on problems when a YA engine with a 7.25 clutch is fitted in a YB which still has the yb bell housing fitted. If you then fit a YA bell housing which is shorter to the car will the yb prop shaft still fit bearing in mind the ya shaft is 1.187 mtrs long and the YB 1.151 mtrs. Is the sliding joint movement of the YB shaft enough to counter the shorter YA bell housing
John YB0263
JC Jebb

The 8" clutch was introduced in July 1951 during the production run of the Y(A) (albeit late on), but the bellhousing front to back depth is the same as for the 7.25" bellhousing. Only the cross shaft was moved back 7mm, and increased in diameter.
R A WILSON

so that tells me that the prop shaft change when the YB came along was purely due to the axle change Thank you
John 0362
JC Jebb

Yes - should have mentioned that !
R A WILSON

So in the BMC gold seal days there must have been two xpag engines on the store shelves, one for each of the models?? if you do have a Y 7.25 clutch mated to a YB bell housing what exactly are the problems you would notice driving the car?
John YB0362
JC Jebb

For the Y/YB/YT, reconditioned engines might have been a problem, as there were two flywheel sizes (for the two clutch sizes), three ring gears (but only two numbers of teeth), and four camshafts, but they did not all change at the same time or engine number. Perhaps Morris Engines Division only kept reconditioned blocks and cranks, and assembled the engines according to what was specified with the order - we need someone who was in the trade at the time to comment.
With a 7.25" clutch and 8" bellhousing, there might be difficulty (excess force) and clutch judder when disengaging the clutch. These problems might ease as the clutch wears - see my previous comments in this thread (posts 8 and 9). Comments would be welcome from anyone with such a combination.
R A WILSON

This thread was discussed between 19/09/2017 and 10/11/2017

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