Seal types - good info

Jon March

Something happened when i was filling my rear hubs with grease after installing new seals. One hub burped grease out the rear seal like it should...but the other hub woudntt - so i kept pumping thinking it just needed a bit more to come thru...and POP! the outer/hub side seal popped out in a blue mess. I forget why, but i think i recall that the shop either installed the inner seal backwards (spring hidden), or i accidentally bought a dust-lip seal which prevented proper grease exiting.
Either mistake could cause this to happen: a seal not allowing grease under pressure to exit properly.

But a question: lets say all the seals were correct: what might cause the same thing to happen? how exactly does grease travel into, and through, a rear hub?
What are the passageways for the grease? and could a grease port/pathin the hub ever be "blocked" to the rear seal to cause the front seal to burst out?

CORRECT TYPE for rear hubs - no dust lip!
outer seal: install with hardside (no spring) showing
inner seal: install spring showing: allows grease to exit near u-joint, not into inner area near brake shoes!

Screen shot 2018-08-18 at 2.21.53 PM.png

You might think a dust lip is a cool idea - but its not in this application: it can prevent grease from exiting and pop a seal completely out if too much pressure is pumped in!

Screen shot 2018-08-18 at 2.21.09 PM.png

And although great on the transmission for the main driveshafts, a double lip seal is also wrong for the rear wheel hubs for the same reasons stated above.

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