[george kujanski]

Regarding sealed bearings: a good friend of mine from my days at Motorola Automotive was the mechanical engineer on the alternator product. He is still amazed at how little grease is required to make the bearings live. For example: the front beaaring in an alternator is a sealed bearing with very little grease. It lives a very long time at high speeds in the underhood environment. Pretty amazing, I think. The axle bearings run pretty slow by comparison. Say with most tires they spin about 750 revs/mile so at 60 MPH that's 750 RPM. The bearing is spinning at 375 RPM; no big deal.

George

[AROWHED]

That is a real good point, George. I as well was always impressed by how long an alternator front bearing can last, in such temperature extremes, tight belt tension, and constantly varying RPM all acting agaisnt it.

But then again, I have fallen prey to a failed sealed rear axle bearing on my 65GP. Noticed a low rumbling sound one day, so drove 2 miles back home, then found the damage. I have no idea how many miles the bearing had prior to failing. But when it did, it forced the press-fit inner bearing race to spin on the axle shaft, destroying it as well. Kinda hard to find 65-70 fullsize Pontiac axle shafts in the salvage yards anymore...or any other part for that matter.

I puleld the rear end off a junk 65 Bonneville a couple months ago. As a test, I pulled one axle shaft out, then removed the axle shaft oil seal from the axle housing. Next, I pried out the sealed axle bearing's INNER oil seal, the one that would face the differential. Then re-installed that axle shaft, bolted a tire on (with no brake drum behind it), then stood the rear end up vertically on that tire. I let it sit that way for about a month, to see if the gear oil would migrate through the bearing and past it's remaining outer seal. Short answer is: Yes, the oil got through it, but it was not a whole heck of a lot. And it was a pretty well used bearing, too...but still had some miles left in her, though.
So the next test will be to try the same in a car that's being driven, with a brand new axle bearing modified as above, to see if the gear oil will lubricate it enough to keep it alive, while not leaking out onto the brake parts excessively.

[george kujanski]

I find it REALLY hard to believe that sealed axle bearings only last 10K miles. I never had to replace axle bearings back in the day......

The bearings also don't need a lot of lubrication. Sure, they need some, but not much. Rolling friction compared to other types is very low, low friction = low heat generation. The lubricant helps lower friction even more plus keeps the seal lubed. What will kill the bearings are contaminants getting in there or water, which will cause rust on the balls and races, and away you go. Overloading the bearing will damage the balls and races also. Excess heat generation will damage the lube and seals; excess heat from dragging brakes, etc. could do it. Sealed axle bearings should easily last 100K. If not, something else is going on.

George