As mentioned the vent not operating could push the seals, however with the green bearings the thrust spacer or block in the differential may need removed. My first thought is that someone pulled the hearings into the housing using the retainer bolts and side loaded the bearings against the spacer in the differential.
This is courtesy of Dr Diff.
http://www.doctordiff.com/blog/tech-info/why-green-bearings/
The need for non-adjustable wheel bearings
Most of these problems can be avoided by installing non-adjustable sealed ball Green wheel bearings. The name comes from the Green Bearing Company which first produced them. The company has since been purchased by Bearing Technologies.
Unfortunately, the original Mopar Green wheel bearing design has 2 problems.
First generation (RP-400) Green bearings, still sold by Mopar Performance and others, are problematic because the crimped-on flange will not allow the bearing to wiggle around inside a housing that is not perfectly straight (none are).
In addition, the design causes the axle to be inserted DEEPER into the housing than necessary. This results in pre-loading against the differential thrust block and early bearing failure.
Second generation (MO-400) snap-ring style Green bearings are forgiving because they can move around inside the housing and they do not preload the differential thrust block in a stock application.
Most guys who have problems with Green bearings are running the RP-400 first generation version or incorrectly made aftermarket axles or housings or poorly designed rear disc brake kits, all of which cause pre-loading and premature bearing failure.
