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1984 R100 65,000KLMS snowflake wheels drum brake
So I've got my wheels off and looking at my rear brake shoes the lower shoes have some oil on them. I cleaned them up and for days, there was no leakage, today there is some. I guess that could mean that the big seal around the splines is leaking. That could be a big job?

You must have got a lemon!
It's hard to believe a seal can dry out and leak after only 40 years!!!
What's the world coming to?

Just get a new seal, pry out the old one and tap in the new one.
No special tools required.
Lube the outer edge of the new seal and just tap it in evenly and gently.
You can use an appropriately sized piece of pvc pipe or reasonable facsimile to tap it in, if you're more comfortable with that.
Wrap some masking tape around the splines so the new seal slides past them easily.

There's also a paper gasket behind that cover, but that rarely leaks.
Make sure all the bolts behind the brake shoes are tight.
In the event that the gasket is leaking too, just remove all the bolts and pop the cover off, clean everything and re-install it with a new gasket. Again, no special tools needed.
I just use a bit grease on that gasket, no sealer. You might get differing opinions on this.
To finish up, rough up the brake shoes with 320 grit sandpaper backed with a hard rubber pad, not your finger tips.

There's also a inner seal, if that one leaks it will be obvious at the tiny hole in the outside of the casing below the axle nut. (edit: on some models)

It's not a big deal to change but it usually lasts 'virtually' forever.

Wow! Full instructions on how to do it...Thanx! Hopefully the dealer will have one in stock. I'll see if he has the paper gasket as well.

Can't seem to find that seal on any parts fisch. Anybody got a part number? It's the seal that goes behind the splines.

Zombie Master wrote: ↑Wed Jun 22, 2022 10:08 pm Can't seem to find that seal on any parts fisch. Anybody got a part number? It's the seal that goes behind the splines.

Pull the seal out and take it to a bearing supply. It's a generic size. That's what I've done in the past.

You need # 3 in illustration
Part # 33 12 1 233 528 GASKET RING - 65X85X10

previously was 33 12 3 004 343 GASKET RING

SteveD wrote: ↑Wed Jun 22, 2022 10:51 pm Is this it? edit: 1 minute... but only 14Kkm away!

This better be a coincidence.
I'll be really pissed off if I discover that your computer is spying on my computer

Zombie Master wrote: ↑Wed Jun 22, 2022 9:34 pm I'll see if he has the paper gasket as well.

1 - I really wouldn't worry about the paper gasket.
It never leaks and only needs to be replaced if the cover is removed.
2 - never say never

If you do indeed absolutely need to replace the paper gasket, I'll give you some pointers to make it really easy.
These are shortcuts only the mechanic from hell knows, but is willing to share with you.
They are nowhere to be found on the internet, unless you have unlimited 'dark web' access.

When I was getting oil in there it was coming through my brake pivot pin, or whatever it's called. It needed new O rings. Pretty easy fix as I remember.

enigmaT120 wrote: ↑Thu Jun 23, 2022 7:54 am When I was getting oil in there it was coming through my brake pivot pin, or whatever it's called. It needed new O rings. Pretty easy fix as I remember.

VERY good point enigmaT120, thank you!
That's definitely an issue on some models, but it's unlikely (if not impossible?) on certain later models.
I don't remember specifically when but the brake pivot hole and shaft o'ring setups were changed at some point to prevent that, but maybe it was just on the monolever or paralever systems?

I thought ZM said "the big seal around the splines is leaking" which is very common for a seal of that age but he actually said "I guess that could mean that the big seal around the splines is leaking".

The best thing is to clean everything up and determine EXACTLY where the leak is coming from.
Regardless, replacing that 40 year old seal is a good idea.