Rear Diff Oil leak

It seemed like a simple oil leak to fix, but I ended up finding four different places that the oil can leak out and fixed all of them.

Flange to casing

Oil was clearly leaking from the front of the rear diff casing and "wetting" the case. There is a major seal part number 40101693 (£26 Vexi). The job involves
Undoing the rear propshaft flange to drop the end of the propshaft out of the way.
Undoing the 36mm nut holding the flange adapter. Forum reports suggest this is very hard to remove, and then the seal comes out easily. I found the opposite. Nut is 36mm and should be torqued to 200Nm, mine came off easily. But the tab needs drilling or prizing out.
The flange adapter then slides off exposing the splines
The seal is a tight fit and needs to be prized off without  damaging the splines or thread.
New seal goes in. It's a tight fit; must go in square and needs a soft mallett or piece of wood to put it in.
Put the flange back and tighten the nut. You could bolt a bar (or unistrut) to the flange to counter the spanner. But I relied on the wheels and handbrake.

Job done? Well no. Oil leaked out and was splattered all over by the propshaft. I dismantled it again and had a think about it.

Splines and thread

Apart from the seal described above. Oil can also leak down the splines. Potentially the flange on the  nut seats well enough. But I added some hylomar blue. And put it back. Oil might still seep through the threads, so a final level of oil seal is the propshaft to adapter join. Again I added Hylomar blue to seal the mating metal surfaces. That did work.

Filler plug
And just for completion, it is designed to seal on the threads. I put PTFE tape around the filler plug.
.
Old seal, shredded because it was so hard to remove

New seal sitting in place
200Nm using a jack to tighten it and unistrut to hold the flange.


Nut seal to top of splines

If any oil leaks past the nut then the propshaft seals against the flange.

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