Practically Classics Forum

Chaps,

My A30 803cc gearbox has presented an oil leak which I have yet to fully investigate. The oil is appearing from the drain hole in the bellhousing (you know, the one with the split pin in. It's either coming through the backplate of the engine or from the input shaft of the gearbox. I strongly suspect the latter as the engine has recently been rebuilt by Classic & Modern in Bracknell and I trust their work implicitly and there is no symptoms of oil on the clutch.

So I have therefore been concentrating my thoughts on a damaged oil seal around the input shaft. Imagine my surprise when I found that the diagrams in my Haynes and original BMC workshop manuals don't show any such oil seal and parts suppliers don't list one. I take it that there isn't one.

Questions: What stops the oil leaking out the front cover? Is the bearing a combined bearing and seal? If it is, can I replace the bearing without completely stripping the gearbox?

Well if it's anything like the gearbox on my 1275 Midget and Morris Minor, there isn't an oil seal, it's a scroll type "seal" that just drives the oil back into the gearbox when it's running.

Mind you there isn't an oil seal on the rear of the crank on a standard "A" series either.....

I've seen most of these leak - worse if you over-fill either the engine or box, or if you park on a steep slope.

Such is life....

^^^WHS^^^

You can often tell which is leaking by the colour - darker stuff tends to be engine and lighter stuff from the gearbox. It's easier to tell if you put a white plastic tub below the hole - not so easy to spot on concrete.

It's a it like my old Fergy (Standard engine of similar era) - if it doesn't leak, you should check to see what's wrong!

Thanks for your responses - definitely gearbox oil.

I suspect whatever damage there is was caused when I refitted the engine. I had been lazy and left the gearbox in the car, so there was quite some jiggling to do when I put the engine back in. No leak before, but leaking after.

I accept that if I'm to successfully fix this, the engine and gearbox will have to be removed, leak rectified off car and then refit as one unit. The big question remains, how do I stop the leak when there is no seal to replace?

KRX756 wrote: The big question remains, how do I stop the leak when there is no seal to replace?

That's what I was trying to explain - you don't. They all leak a bit.

I'm unsure of what you mean by "damage" - yes, if you've caused damage then you need to see what that damage is, and repair it, we can't really comment without knowing what the nature of the daamage is. However, personally I'd be surprised if it's actually damaged in a way that makes it leak oil....

Regarding the input shaft, there's nothing you can do to stop this leaking as far as I am aware, that's how they are.

Only other thing I can think of is that the gearbox housing gasket inside the bell housing is leaking, but this would be all guesswork, you'll never know until/unless you take it apart again. Your call!

Cheers

Have you checked the gearbox oil when on level ground ?
It might simply be over filled ?

Paul H

Thanks again for your comments. I'm merely trying to work out in my head what the problem might be - clearly I will be removing the engine and gearbox combo and all should be revealed, just at the moment, I don't quite understand. Just letting it leak is not an option.

All I know for certain is that it didn't leak before fitting the engine, now it does.

I'll let you know what I find.

Regards,

KRX756

KRX756 wrote:..... it didn't leak before fitting the engine, now it does...

Perhaps you didn't mean that, but is it not more likely that it would leak with an engine fitted? Especially one with no physical barriers to oil finding its way past the rear main.

If it's an A series, it will leak from there, as , as stated, there's no seal. There is a reverse thread on somewhere that attempts to screw the oil back in, you can probably see how well that works. If it's a small leak, don't worry about it, if it is the engine it won't get on the clutch 'cos the flywheel's in the way. If you really must stop it leaking there's a rear seal kit available, either from Moss or Peter May engineering. It's 100 quid +VAT from Moss though - that's a lot of leaking in my book...

KRX756 wrote: All I know for certain is that it didn't leak before fitting the engine, now it does.

Could I paraphrase that slightly and state: "it didn't leak until I refilled the oil"??
I've seen many components in my time that didn't leak, as there was very little oil in them, but on rebuild and refilling they started dripping. Possibly it would have leaked before had the oil been topped up? In my garage a car that doesn't drip slightly requires oil - there's none left to run out!