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MG MGA - Rear hub oil seal

I wonder why the O-ring is necessary to seal the oil in the rear hub (item 54 in attached image)?
Why is just the paper gasket not sufficient?
The O-ring was introduced as a modification after production had commenced (see Workshop Manual).
The Twin Cam which was introduced after the modification to the pushrod cars does not have this O-ring.

Mick

M F Anderson

The Twin Cam rear axle, without the O-ring, is shown in the attached image.

Mick

M F Anderson

Interesting, Mick.

The function of the O-ring may just be to prevent oil leaks when the brake drum is removed, as there is just one screw holding the joint together at that point.

When everything is bolted up tight, the gasket should be able to do the job, as you say.

The O-ring was also used on the smaller axle, as fitted to Morris Minor, A35, Sprite and Midget.
Dave O'Neill 2

Hmm
Interesting as you say
I notice that the TwinCam drawing doesn't show a bearing spacer either, it may possibly be built into the back face of the adapter-49
In both instances the gasket thickness is most important to get the correct preload on the outer bearing shell
It's not 'just' a gasket
I'm wondering if the O ring was introduced to stop oil weeping past the gasket when the hub is set up with maximum squish .004"
The gasket wouldn't be over tightly held at that -- just a thought
willy
William Revit

I believe you are right that the problems was, and can still be, oil leaking into rear brakes. I for one have had this issue even with O rings.

One thing I read once, but no one else seems to know about, is that sometime early in the life of MGAs they dropped the level, and hence quantity, of the oil in the diff by lowering the position of the filler. This was supposed to have been done to solve same oil leaking issue. Perhaps this was done at same time as O ring was introduced.

Paul
Paul Dean

Willy

Interesting that you mention the spacer.

When I saw that, I had to look it up to see what it was. Spridgets don't have it, and neither does my banjo-axled MGB, as it has wire wheels.
Dave O'Neill 2

hi I have MGA which is relatively early, being 1957 and it has the groove and o ring, so they must have introduced it fairly early in the manufacture.

I personally would rather have it than be without, I was initially disappointed when pulling the hub etc. apart, then I found it under the gasket I had to scrap off, and felt quite relieved that it was there.
( may just be a belt and braces attitude on my part)

Ross
rw mcintosh

My reference just says "later 1500". Also interesting to note that the earlier cars had right hand thread on all four knock-on hubs. Presumably oil leaks and wheels coming off had an influence in model development.
Graeme Williams

Not for the knock-ons. Knock-ons were always LH thread on right side of the car. Early cars had right hand threads for all rear wheel bearing retaining nuts (later changed to left and right threads).
barneymg

Ross,

The rear axle O-ring oil seal introduction is quoted in Section H10 of the Workshop Manual (attached).
However there is no direct link between the rear axle number and the VIN (chassis number).

Mick

M F Anderson

The location of the rear axle number is shown in the attachment.

Mick

M F Anderson

"However there is no direct link between the rear axle number and the VIN (chassis number)."


If anyone has a Heritage certificate for an early car, it should include the axle number. It may be possible to narrow it down.
Dave O'Neill 2

Yep, misread it Barney. It did refer to the nuts on the axles now I read it more carefully. Apologies
Graeme Williams

Hi Dave,

I have a Heritage certificate (recently obtained) - there is no mention of the axle number of my 1958 Coupe.

Regards,
Phil
T Gee

This thread was discussed between 20/08/2017 and 21/08/2017

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