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MG Midget and Sprite Technical - Rear diff oil leak. Can this end up in the rear h?

Hi,
My 59 frog rear brakes were out of balance so took it in expecting leaking rear slave cylinder.
Garage reports that there is an oil problem on the pads but does not think it's from the slave cylinder. Instead the mechanic is telling me it's from the rear diff. Coming down the half shaft.
Is this possible?
Steve
Steve 59 Frog

Yes. The oil in the differential does ride up the half shafts and if you've got oil on the brakes, that means that you've got bad seals at the hub. Either the one that rides against the axle housing or the hub to half shaft seals.
Martin

Replace the O-ring and paper gasket; be meticulous about cleaning the mating faces and also check them for flatness.
David Smith

Steve,

As above, there are 2 oil seals in the rear hub. On the inside there is a conventional lip oil seal, and in addition there is an 'O' ring that fits between the halfshaft flange and the hub face, together with a paper gasket that fits next to the halfshaft flange.

You need to replace all three seal components to be sure!

The attached picture shows the relevant details.

Richard



Richard Wale

Early cars, and possibly in a 59frog, used a felt seal for the inner one that runs on the end of the axle. Later replaced with the lip seal in Richard's illustration. The advantage of the felt seal is that they don't wear a groove in the axle casing surface, as the lip deals eventually do. New felt ones are NLA but can be replaced with the modern version.

If doing this job yourself, Jack just one side of the car at a time. Get it reasonably well off the ground and oil will run down inside the axle casing so it won't overflow as you work on that side and no need to drain the diff oil. Remove roadwheel, and brake drum. No need to remove the shoes unless they are oil contaminated and also need replacing.

Then BEFORE you clean anything down inspect really carefully to see if you can trace exactly where oil is leaking. If you are lucky it will be from the half shaft flange joint only, which makes for an easier repair. If it is leaking from behind the hub where it is closest to the backplate then the hub itself will need removing to replace that seal. In which case consider fitting a new bearing at the same time (around £10 per side, so probably worth it)

Remove small countersunk screw which aligns the half shaft flange and pull the half shaft out. If the leak is only at that flange you can just clean down and reassemble. Make sure you use the correct thickness of paper gasket as this determined the clamping effect on the wheel bearing.

If the hub oil seal needs replacing you will need to undo the large hub nut and remove the hub itself. Inspect the axle casing where the seal lip runs as they are often damaged. Simplest repair if it is is to use a Speedisleve.
GuyW

In the early days of Sprite ownership (mid 80s) I decided a precautionary change of rear wheel bearing made sense. However, I found the new bearings, while ok, had slightly more play than the old bearings which I'd replaced. So consider a bearing change but if the existing bearings are ok, leave them in.
Daniel

I’ve had a similar experience with play in new bearings, even with Unipart bearings from the 1990s.
Dave O'Neill 2

You can get sealed bearings, they are lovely:
SKF part# 6207zz
NSK part# 6207vvc-mav2

I use silicon sealant on both sides of the paper gasket.
Before I use the countersunk screw I clamp the half shaft with the 4 wheel nuts. I use bigger nuts under the wheel nuts as "distance pieces"

Flip


Flip Brühl

Flip,

I think it has been mentioned before that the SKF 6207zz is a dual shielded bearing rather than a sealed bearing, that would be a 6207 2RS. The shields don't prevent a flow of oil through the bearing but do keep out larger contaminants.

Bearing can be bought with different internal clearances if desired.
David Billington

I believe if the problem is with the lipseal (inner side of the hub) the oil won't get in to the brake drum. If it is inside it will be the o ring/gasket assembly leaking which is in my experience a fairly weak arrangment since removing the wheel removes a major clamping force leaving only one or perhaps two countersunk screws holding it together.
Even if you take up the suggestion of tilting the axle up, away from the hub (very sensible) there is always enough oil to run out from somewhere to contaminate the shoes. I have used a plastic "bib" to cover the shoes to protect them.
Two other regular issues: Remember one of the hub nuts is left hand thread (I recall it's the nearside -but check) and don't ask what torque to retighten! Wasp nest that one!
Graeme Williams

Graeme,

If the oil seal leaks then the oil leaks out between the backplate and the brake drum so into the brake drum. This gives 2 possible leakage paths which are easily addressed. As mentioned earlier if the surface the oil seal runs on is badly worn it can be remedied with a speedisleeve.
David Billington

Just done mine today with a speedie sleeve hope it stops the oil leak.

mark heyworth

think this may be why my brakes where not as good as they used to be all covered in oil

mark heyworth

will this be tight enough using this

mark heyworth

Good and tight that’s enough.
The returned

You need a track day and a K series to get a proper leak going on. Disaster.....

This was caused by hard cornering at Croft flexing the hub/bearing and opening up a gap in the oil seal on the axle. So much flex, the drum had caught on the backplate at the bottom.

Also - if you can hear diff whine through a helmet - the diff is wrecked.

Rob Armstrong

'You need a track day'

Yes, we had exactly the same experience early on after fitting the 1380 engine into our Minor.

At that time we were running Yokohama A021 tyres (no longer road-legal), and were on the MSA Euroclassic in 2001. We had just finished a fair few laps of the Imola GP circuit, when after getting back to the pits, I noticed a small amount of oil on the RH rear wheel. Checking the other side was the same oil leak.

The rear bearings and seals were at most 10,000 miles old, and on stripping the rear hubs, both oil seals were completely shot.

After fitting new bearings and seals, courtesy of one of the other participants, we finished the run and the trip back home, but then fitted the Peter May double bearing hubs. With more support to the hub, we have had no leaks at all after around 50,000 miles, with one precautionary bearing and seal change 2 years ago.

Richard
Richard Wale

This thread was discussed between 03/06/2018 and 06/06/2018

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