Rear bearing eater

Yep rear wheel bearings are a weak point. 
The rear wheel bearings have no independent seal, just the seal on the bearing itself. The seal on the inside that runs on the retainer is only to stop gear oil leaking out into the drum brake.

It's a stupid design. 

My theory:

The bearing is a C4 clearance, "normal" bearings are CN (normal) but they're never usually specified as such on the bearing, and standard high clearance bearings (as found in electric motors) are C3, so these bearings are very high clearance. The extra clearance means the seal OD is not concentric to the ID, so does not fit as tight on the bottom half of the bearing. 

The seal from my observation is not usually very tight anyway, and moisture, brake dust, and general rubbish easily gets past this seal. Especially if it is submerged or in a dusty / sandy area. (Both of which apply to me) There is little room for grease in the bearing and no way to flush impurities out, so there it stays, chewing away at the races in the bearing until it ultimately fails. Usually in my case it seizes up when parked and spins on the axle, chewing into the bearing diameter. 

My Jimny currently has 1 x working rear bearing and 1 x is effectively now a hardened steel bush. Have been driving it like that for a couple weeks as I haven't had time to change it. You get used to the squeaking for the first couple minutes driving till what's left of the grease makes its way in. 🤭

I do river crossings and beach driving pretty regularly, so I go through a lot of rear wheel bearings. I've tried OE parts, expensive aftermarket, cheap aftermarket, I've removed the rear cover and added extra grease, I have also tried running a V-ring against the backing plate to keep most of the rubbish out but nothing seems to work. 

Now I just get the cheapest bearing kit I can find (about $60 - $80 NZD here) and always keep one on hand.

As I mentioned, the bearing usually spins on the shaft which means I have to machine down the bearing diameter, build it back up and remachine it to original size. Then straighten if needed.
I have once machined it a couple hundredths over to maybe get a better grip on the inner race of the bearing but that just made it even more difficult to install the bearing. 

At least I'm getting good at replacing them, the most pain is the drum brakes.
I do each side not quite twice a year, maybe 3 times all up between both sides. 

One of these days I will come up with a better sealing arrangement but usually I'm in too much of a hurry to get my vehicle going again to stop and take a good hard look with the whole setup apart. 

Hi. 1st time I here had the usual noise, and was oil all over the rear wheel, dripping from the drum. Ran it a bit longer until the noise was too bad. Drove very slow back to Calais, and happened to find a garage that would do it, but too late to finish the planned trip. This time, was only 100 miles from Alps (so carried on to my 1st planned stop on edge of Alps), got oil dripping from drum again. Only slight noise at the moment, but did not dare risk going my planned route on the old military roads. Steep hills and a brake missing is not good (I have trailer also).

Having had 1985 SJ with more or less the same bearing design and a later jimny since 1997 or so I have changed these bearings some times. I do some sandy and muddy offroading and, salted winter roads wich is worse than most offroading.

I think I done the rear wheel bearings once on the SJ and once on the Jimny. But also changed to spare used axle shafts with used bearings a few times.

I allways put in the original bearing or SKF. Once i did a chinese bearing and that is the only total fail I had. It just disintegrated after 6 months. Crushing and grinding and could feel the car hopping in the rear and the pedal pulsing as the shaft spun around in the axle housing.

My jimny have had the bearings starting to make noise and leak oil at approx 110k to 130k km and the SJ too.
i have had large to very large tyres, a heavy foot, a loaded vehicle, and often a trailer.

When C3 is the spec there is most likely a reson for it that most bearing suppliers and engineers know well.
it could be alignment or temp differences. I would not change that.