When I went out to work on the truck on Sat, I saw fluid running down the bottom of my rear, passenger side rim. So I pulled the rim and drum and there is fluid puddling in the drum and then running out. It is yellow so it has obviously mixed with water (which is understandable with the snow and mud) so I couldn't really ID it by look. I'm wondering how to figure out if it's the brake cylinder in the wheel or the axle seal leaking (which I believe could leak like that). The only thing that seems to be wet is the adjuster at the bottom. But it had sat for about a week. If it's the clyinder, it might explain the spongey brakes and pulling under hard braking. What can I do to test it? Thanks!!