I replaced the wheel bearings on the left rear a couple of years
ago due to strange rumblings and the apperance of alot of fine
metal dust every time I pulled off the hub cap. This cured the rumbling
for a bit but the production of metal bits eventually continued and
finally so did the rumbling. It got louder and louder (unless you did
a fairly fast left hand turn, in which case the weight came off the wheel
and it was lovely and quiet), until I was forced to do something about
it. 

The bearings didn't seem to wobble when I pushed the wheel round, but
I thought I'd better take a look anyway. When I removed the brake drum 
(big one piece cast one on the '70), I found that the splines were 
about half the normal amount (I kid you not), which explains where 
all the metal dust was coming from. Basically I don't think the 
previous owner had tightened up the axle nut properly, allowing the 
drum to move around and so no splines. Even though I had the nut 
tightned correctly when I replaced the bearings last time, the damage 
was already done and the drum continued to do move around. I continued
the strip and checked/rebuilt the bearings anyway, but they were fine
and the rumbling seems to have ceased.
 
So bus owners, make sure that nut is *tight* or its new drum time!!
-- 
__
Marcus Grant
mty016@uk.ac.cov