Leaking gearbox gasket

[daglocks]

My 1936 4 speed gearbox has a small triangular (Shaft bearing?) cover behind the clutch operating shaft.
I tried to remove it to change the gasket, but its stuck. Is it safe to remove it without stripping the box, and if so, how?

[Chris KC]

Hi,
I presume the gearbox is out of the car?

My first question would be why change the gasket? If the area is oily, are you quite sure it's leaking from this cover? It's just as likely to be coming from the 1st motion shaft bearing or indeed the rear main of the engine; or even drifting down from the block to crankcase joint... I could go on.

The 'cover' in question is the front layshaft bush. I'm not 100% sure without going out into the cold & dark to check, but I think to remove it you would have to first remove the clutch pedal shaft, which in itself is not something I'd undertake without a jolly good reason. It's conceivable that you might pry it out far enough to get some sealant in the joint, but I'm not sure I'd recommend it.

If this is a 'running repair' I'd suggest to leave well alone until you are ready to undertake a more extensive gearbox overhaul. There's no shame in a little weeping of oil. If however it is pouring out a more extensive overhaul might be called for.
In this case I would direct you to Harold Perry's account of a 4-speed box stripdown in 'The Austin Seven Companion', which tells you pretty much all you need to know. It's not especially hard to strip and rebuild a 4-speed box as long as you proceed carefully and methodically.

[Speedex750]

Hi Daglocks,

Chris is right; the piece in question is the front layshaft bush, it's a top hat shaped bush into the gearbox casing. The tapered pins for the clutch release shaft usually knock out quite easily, just make sure the end isn't bent and you're knocking it in the right direction. With the gearbox on the bench it should be possible to remove just the bush and regasket it, tap it rotationally with a hammer and drift before trying to extract it. The layshaft should be supporting itself from the rear.

But as Chris says; make sure this is where the oil is coming from first!

Hope of use, Dave

[Ruairidh Dunford]

Andrew,

I have been following your parallel (illustrated) post on Facebook as well as the one you have here.

Are you certain the oil is coming from the gearbox? It is quite common for Austin Sevens to leak from the flywheel (lack of) seal, this manifests in a small pool below the gearbox every time you stop the car.

A test would be to fill the gearbox with fresh clean oil, drive and then check the spillage - if black it will have come from the engine side. If clear, the gearbox.

[Chris KC]

Hi Daglocks,

Chris is right; the piece in question is the front layshaft bush, it's a top hat shaped bush into the gearbox casing. The tapered pins for the clutch release shaft usually knock out quite easily, just make sure the end isn't bent and you're knocking it in the right direction. With the gearbox on the bench it should be possible to remove just the bush and regasket it, tap it rotationally with a hammer and drift before trying to extract it. The layshaft should be supporting itself from the rear.

But as Chris says; make sure this is where the oil is coming from first!

Hope of use, Dave

I'm not sure whether you've been lucky Dave or perhaps I just don't have the knack; but in my own experience those clutch shaft pins can be an utter beast to get out.

Otherwise I agree, but whether replacing the gasket will stop the leak is another question! I'd certainly advocate a modest smear of sealant either side.

[Speedex750]

Oh; and the thickness of the gasket is used to set the end clearance of the layshaft gear. A little thinner or no gasket would probably be OK as most have worn the clearance larger. I agree that a sealant would help if you're certain this is the source of the puddle.

Dave

[Chris KC]

Yes Dave, must say that thought crossed my mind too, I just wasn't 100% sure without seeing it in front of me. Shouldn't be a problem if new gasket thickness is roughly same as old.

---

p.s. on my car I get worried when I find places that oil ISN'T leaking from!

[Robert Foreman]

If you choose to remove the triangular cover be very careful because it is hardened. If you remove the three screws and try to drift it there is a very good chance of breaking off one of the ears on the flange. 
   The only safe way to do this is to heat the gearbox casing up with a hot air gun until it is quite hot.

[daglocks]

Thanks for the advice chaps. Mission accomplished! she was a stiff fit, but new gasket now installed.