HELP...please.... rear wheel bearing tips on installing

[caddydaddy]

Hi all, 8 months ago I had my rear wheel bearings replaced by my trusted mechanic who works on many USA cars, he replaced my old rear wheel bearings with ones I purchased, but within days the passenger side started to leak, for another 3 weeks or so it did, then it stopped, months passed and then I would hear the old familiar sounds of the bearing groaning, surly not, not just after 8 months, anyway that followed by the drivers side started to leak and the noise is worse and to a point as where I can hear the grinding, so no more driving. Now I have bought my new rear wheel bearings from RockAuto and had them shipped over here nice and quick, the prices were weird, starting from $7.89 to $84.99 depending on the manufacturer, kinda weird, why would you go for the cheaper one?
Anyhow I purchased the more expensive ones the SKF  RW509FR, so I hope these are the good ones, (still made in China) the others I have to get my mechanic to take out now, does anyone think I may of got a bad set of bearings? My mechanic seemed to think they come of the axles ok, and when on ok, but he though there should have another seal? Although when you look at the bearing it is all sealed, like all one unit, and the collar. So any tips for my mechanic to watch out for this time? I don't want to have to replace another set before the end of next year, I want at least a decade out of them. Any tips?
Regards CaddyDaddy

[blue68deville]

The seal is built in to the bearing. Maybe he installed them backward. The seal keeps the rear diff oil out of the bearings, they are self lubed with grease when made.

[Ronald]

Check for the usual causes for leaks.

Wear ring on axle shaft that would require shimming the new seal so that it has a new sealing surface.

In the process of removing the old seal - the outer seal area has a gouge in the axle housing that allows for seepage.

Was the shaft dragged across the seal during the install?

Was the new seal and shaft coated with oil - if not it could run dry until grease sloshed to the right places to lube things.

No leakage is acceptable after new seals are installed!

If it leaks again - take it back to shop asap before the bearings are damaged.  The bearings can be repacked with the shields in place with a bearing packing tool.

Ron