When you get the drum off, your nose will let you know if it’s gear lube. Also a lot of time if it’s the wheel cylinder the boots will be swollen and if you peel them back, they will be wet with brake fluid inside. I highly recommend these seals.
SKF 34384 Rear Wheel Seal https://www.amazon.com/dp/B000IX2BCO?
There are cheaper ones, but these are nearly fool proof to install.
Some people say you should always replace brake shoes after they’ve been wet with gear oil, but I’ve had decent luck cleaning them. If they have plenty of life left, I would just make sure you have plenty of brake cleaner on hand. If they’re getting thin, it’s probably just as easy to replace them.
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