Jim Macklin wrote:
Prop seals leak because people use the blades as tow-bars on
the ground. Front crankcase seals leak because of blocked
case vents.

That's a gross oversimplification. As I said, the old
Hartzell prop seals go because they are life limitted to
a few years. They aren't even anywhere near the blades.
While there's grease up there in the blade hubs, there
ain't any engine oil.

Had a crankcase seal blow out because the case was misassembled.
Had nothing to do witht he vents.

In-flight, centrifugal forces make the pressure on the seals
at right angles, does not cause leaks.

What?