I installed axle repair bearings on my Ford 8.8 axle today. Everything I could find online said to install them seal side out. The ones I got however have two seals. Why would the axle repair bearing have two seals?
Axle repair bearings are used when the surface of the axle is chewed up by the old bearing. The repair bearing moves the location of where the bearing rollers ride to a smooth location on the axle. Depending on the vehicle this relocation may not leave enough room for a proper axle seal on the outside of the bearing. In these cases the seal is relocated to the inside.
This leaves a problem, there is nothing to lubricate the bearing. In the standard axle setup the gear lube fills the bearing. With the seal now between the bearing and the gear lube, no lube can get to the bearing. The way this is solved is they pack the bearing with grease. To keep the grease dirt free a dust seal is installed on the outside.
In this way the repair bearing will have two seals, one on the inside and one on the outside.
In my case (Skoda Estelle '72) it comes with two oil retainers, on each side of the bearing: the inner one stops oil from the gearbox, which flows inside the semi-housing tube to cool the axle and as residual to lubricating the axle/differential link. The outter one stops the thick grease that lubricates the bearing.