Wheel cylinder or axle seal leak?

[BobSacamano]

The third picture is from the other side after I took the brakes out

 

[SenorNoob]

That doesn't look as wet as I'd expect for an axle seal. But if the wheel cylinder was leaking that much, you probably wouldn't have brakes.

I see the axle is out of the truck. I'd probably do both while it's apart. Likely wheel bearings too... (It can be difficult to get the seal out without pulling the bearings.)

 

[BobSacamano]

I just bought it. The previous owner said it had been out of the truck for about a week. He had told me a wheel cylinder was leaking on one side, but both sides look really bad. I’ve already dumped the gear oil and put the cover back on, but I haven’t put new gear oil in yet.

 

[helpme]

Mix some Bar's Stop leak when you replace the gear oil. The Stop Leak will cause the seal to swell and stop the leak. Make sure your vent tube isn't plugged!

 

[Shran]

Axle seals are easy to do and cheap. Just make sure there isn't a big groove worn into the shaft. Sometimes you can clean that up with emery cloth, sometimes it's just hopeless and you will need a new shaft. They make repair bearings but every time I've seen one of those used, it still leaks right away.

This one looks more like a wheel seal leak to me though, it's not a horrible ugly oily mixture of brake dust and gear lube. If it smells like sulfur, it's gear lube.