Leaking Differential Pinion Oil Seal in my 1950 MM

[dschwartz1957]

In November 2022 I stored my 1950 Morris Minor Tourer in the garage for the winter. In March 2023, I noticed a large oil stain on the garage floor under the differential, with drops of oil in several places on the underside of the differential. Previous oil leaks were only under the engine, so this stain was new. I recently cleaned the outside of the differential so I could check the oil level. The oil was almost empty, and oil continues to drip from the bottom of the differential. Oil is also spattered on the underside of the car above the propeller shaft. Attached are several files showing the leak.

I have read numerous posts in the MMOC technical forums about differential oil seal leaks, and ordered a replacement part from ESM.

https://www.morrisminorspares.com/rear- ... le-p831244

The forum posts have all been related to the later differential and oil seal. My car definitely has the early split-casing rear axle, though a previous owner swapped out the side value engine for an A series 948.

I plan to replace the oil seal without removing the rear axle. Obviously I need to remove the propeller shaft to access the pinion bolt. I am concerned about being able to loosen the pinion bolt without the wheels turning. The parking brake works well, but probably won't hold if the bolt is really stuck. I plan to put the rear wheels on ramps and chock all four wheels.

Is there anything specific I should know about replacing the pinion oil seal on an early split axle?

Thank you,

David Schwartz
Framingham Massachusetts (near Boston)

[oliver90owner]

Can you first confirm that the oil level was not excessive and that the axle breather is clear, before committing to wax is likely a not too arduous replacement.

Are there other issues with the rear axle, as the amount of oil on the casing seems to indicate it was leaking a while before being stored.

[svenedin]

I had this job done for me (ESM) on my later car (1969). I actually watched the mechanic doing it. I was told that sometimes just a new pinion oil seal is not enough and a repair sleeve is needed if there is excessive wear. In my case it was just the seal and all is well. I had quite a puddle under the diff. The old seal was ancient and the rubber was almost iron-hard.

[dschwartz1957]

The oil level was fine (not over-filled) when I last checked several years ago.

My car is a 1950 with the early split axle, which does not have a breather.

There are no other issues or leaks that I am aware of. I removed the left rear wheel and brake drum to check for leaks around the axle seal. Everything was clean and dry.

I agree, there is a lot of oil on the diff casing. So it was probably leaking during the 2022 driving season. I didn't notice until I saw the oil stain under the car in March 2023. There is a drip pan under the engine and transmission, but I never needed one under the diff before. We had some very cold weather in New England last winter (-10 Fahrenheit for several nights) which may have caused the seal to contract enough to cause a puddle. My '68 Mini had a brake cylinder leak one winter and brake fluid was visible on the front of the wheel. So the cold does impact old seals, especially on cars that were not driven much in the years before I owned them.

Can you first confirm that the oil level was not excessive and that the axle breather is clear, before committing to wax is likely a not too arduous replacement.

Are there other issues with the rear axle, as the amount of oil on the casing seems to indicate it was leaking a while before being stored.