Hints and Tips - Oil Seals

From: David Cochrane
Date: Fri, 19 Feb 1999
Subject: A7 gearboxes

Mano,

Some time ago you mentioned that you were looking into finding a modern oil seal for the front of your gearbox - did you have any luck with this? I have been washing out the Cup's gearbox with paraffin/petrol and it leaks out the front and back. I'm not sure if this is because it has felt seals which are worn or oil return threads and throwers (which wouldn't work when they're not whizzing round). I wonder if anyone knows how to tell without dismantling the gearbox?

Regards,

David.


Date: Mon, 01 Mar 1999
From: Mano Nadarajah
To: David Cochrane
Subject: A7 Gearbox

David,

My 1927 Three speed box 500 miles later, though early days, seems to be holding up OK. The modern seal I used was 40 x 72 x 8R21. The R21 may be the spec. where the steel outer was not covered by rubber. You may have to adjust the width of the seal on a stone to suit the overall depth available within the front cover (A). See Doug Woodrow Fig C-26 on page C1-18. The Distance piece (D) pushes up against the Roller bearing housing (B) which in turn pushed up to the felt seal via a washer. All you discard is the old felt seal which on mine seemed well cooked. Re-assembly as per usual warm up the cover in an oven or with a hot air gun used for DIY paint stripping.

Make sure that the gasket face of the Cover (A) does make good contact with the gearbox if not you have not taken enough off the seal face! Finaly block the drain hole (if yours has one) on the under side of the Cover (A) with Araldite or similar. This presumably was there to let the oil drain onto the clutch! Just make sure that the breather hole in the gate change assembly is clear.

Furthermore I have also replaced the felt seal in the Crank rear bearing housing with a modern 72 x 40 x 8 seal. You have to have a step machined onto the bearing housing to take the OD - not drastic. In this instance you would discard the felt seal and a steel washer the same diameter as the seal (if yours has one).

> I have been washing out the Cup's gearbox with
> paraffin/petrol and it leaks out the front and back. I'm not sure if
> this is because it has felt seals which are worn or oil return
> threads and throwers (which wouldn't work when they're not whizzing
> round). I wonder if anyone knows how to tell without dismantling
> the gearbox?

I have not attempted any mods on the back cover but I would guess its just the felt seal that needs replacing.

Austins to you
Regards
Mano


Date: Thu, 04 Mar 1999
From: Mano Nadarajah
Subject: RE: A7 Gearbox seal - correction

David

Well spotted! Hadn't recovered from night out. Or perhaps my failing / filing system?

> Mano,
>
> > The modern seal I used was 40 x 72 x 8R21. ....

> Erm, well yes. Or rather, no, because I got one of these, and it is
> nothing like the size I need. The felt seal I have extracted is
> 1 7/8" OD, 1 1/8" ID and 5/16" thick.

The 72 x 40 x 8R21 is for the Crank.

You are correct the second one is for the gearbox front cover. You may quote it in Imperial as your local bearing supplier will recognise it. The 5/16" thickness would squash down (to less than 8mm) hence the minor fitting work required.

Regards
Mano


From: David Cochrane
To: Mano Nadarajah
Date: Mon, 22 Mar 1999
Subject: Re: A7 Gearbox oil seal

Mano,

I thought that I would bring you up-to-date with my progress on fitting a modern oil seal to the front of the gearbox for the Cup. I found a couple of good suppliers of bearings & oil-seals near here, and they were quite happy to handle the sizes in Imperial measurements. The seal I used was 1.125 x 1.875 x .375 R21. The R21 is the spec. where the steel outer is covered by rubber. I got the size by measuring the old felt seal taken out of the gearbox, which was 5/16 thick, but they couldn't supply that. However, 3/8 thick was fine as I left out the felt seal retaining washer (which I didn't need anyway with a modern seal). I had to make sure to fit the seal the right way round, i.e. with the 'open' bit facing where the oil is coming from.

> You may have to adjust the width of the seal on a stone to
> suit the overall depth available within the front cover...

I didn't have to do this - it seemed to be an exact fit.

> Finally block the drain hole (if yours has one) on the
> under side of the cover ...

I didn't have to do this either - the seal covers it.

Thanks for your advice - I wouldn't have started on this if you hadn't mentioned it - finding and fitting modern oil seals was much easier than I supposed. I got mine from Gem: 01926 497778.

Regards,

David.


From: Guy Weatherall
To: David Cochrane, Mano Nadarajah
Subject: Re: A7 Gearbox oil seal
Date: Mon, 22 Mar 1999

A couple of warning words on fitting modern seals, they may not apply in this case but they do apply to A7 hubs.

The Austineers did some work on my back axle. On dismantling it they found that whilst lip seals had been fitted to the rear hubs, the person that had done the conversion had left the running surface un-luricated - they need a smear of grease. In this case the lip caught on the running surface and it ripped the lip off the seal.

The other thing they found was that the old felt seal retaining plate had been thrown out. Apparently the retaining plate helps locate the bearings so you must not leave them out even when fitting the modern seal - so the Ausinteers found a couple and fitted them for me.

As I mentioned, these may not apply to this particular instance but they are worth bearing in mind if you are replacing felt seals with lip seals.

Regards

Guy
28 Chummy


Date: Tue, 23 Mar 1999
From: Mano Nadarajah
To: Guy.Weatherall
Subject: Re: A7 Gearbox oil seal

Thanks for the useful tips Guy.

I hope that there would be enough oil swirling around behind the gearbox front cover oil seal to keep the seal lip happy. Nevertheless it would do no harm if anyone else does attempt this to smear some grease as suggested.

David

On the point of the felt seal retaining plate. When I dismantled the front cover the outer race had its shoulder facing the distance piece (gearbox side). Therefore I had to put the felt seal retaining plate back in behind the open end of the oil seal in order to prevent the rollers from falling out of the race (end without the shoulder) and fouling the oil seal. Was your roller bearing race the other way around? If that was the case it seems like a much neater solution as long as the distance piece has a high enough shoulder to retain the rollers within the race.

Regards

Mano Nadarajah


From: David Cochrane
Date: Tue, 23 Mar 1999
Subject: Re: A7 Gearbox oil seal

> A couple of warning words on fitting modern seals, they may not
> apply in this case ...
>
> ... lip seals ... need a smear of grease.

Thanks - now you tell me!! Luckily I had greased the seal lip and the shaft it runs on.

> The old felt seal retaining plate helps locate the bearings so you
> must not leave them out even when fitting the modern seal.

In the case of the gearbox front seal it is the thickness of the felt seal + washer that locates the bearing outer race. This is the same thickness (i.e. 3/8") as the modern seal I fitted.

Regards,

David (1925 Chummy)


From: David Cochrane
To:Mano Nadarajah
Date: Tue, 23 Mar 1999
Subject: Re: A7 Gearbox oil seal

> On the point of the felt seal retaining plate. When I dismantled
> the front cover the outer race had its shoulder facing the distance
> piece (gearbox side). Therefore I had to put the felt seal
> retaining plate back in behind the open end of the oil seal in order
> to prevent the rollers from falling out of the race (end without the
> shoulder) and fouling the oil seal. Was your roller bearing race
> the other way around? If that was the case it seems like a much
> neater solution as long as the distance piece has a high enough
> shoulder to retain the rollers within the race.

Oh, b*gg*r.

David


From: Michael Lunch
Sent: 13 June 1999
To: British-Cars-Pre-war
Subject: A7 Gearbox - three speed - oil seals?

I am getting very very close to finishing the rolling chassis. Sorted the cardon joint this weekend, fabric coupling in place, brakes, suspension all done. Now for the gearbox...

All advice has been - "leave well alone unless it is broke". I am pleased to follow this advice - one less job!

However, should I worry about oil seals - seeing as it is easy to get at NOW, but would be a right s*d in a month or so time!

What does the team think? (No clues during strip down - everything was so hugely oil covered that I could not tell where the heck it had all come from!)

What other things have I forgotten - that will become far more difficult with body on!

Mike


From: David Cochrane
Sent: 14 June 1999
To: Mike Lunch
cc: british-cars-pre-war
Subject: Re: A7 Gearbox - three speed - oil seals?

Mike,

> I am getting very very close to finishing the rolling chassis. ...
> Now for the gearbox...
> All advice has been - "leave well alone unless it is broke". I am pleased to
> follow this advice - one less job!

Well, yes, provided it is not too worn inside.
> However, should I worry about oil seals - seeing as it is easy to get at
> NOW, but would be a right s*d in a month or so time!

Yes, especially the front one, which will leak oil into the clutch if it is worn. I did quite a lot of research on this, helped by Mano, and I think I have eventually got it right after a couple of false starts. The oil seal you need is a 1 7/8 x 1 1/8 x 5/16 R4. Use a smear of silicone sealant to bed it into the housing, and warm the housing in a moderate oven before assembly. Makes sure you fit it the right way round, ie the "open" bit facing in to the gearbox. Doug Woodrow's book has a lot of info on how to fettle the gearbox. Do not leave out the felt seal retaining washer, as its main purpose is to keep the rollers in place. Put a smear of grease on the rubbing surface. I got mine mail-order from G.E.M., 01926 497778, ask for Steve. The rear seal is a lot more difficult to fit, and I'm afraid I chickened out of doing that - I hope I don't regret it later!

Regards,

David Cochrane

Rugby, England.


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