I found the solution. It was the wheel bearing on the other side. This car is relatively new and tight enough that I couldn't tell what side was causing the problem.
"2008 Forester 85k miles. I had an intermittent serious rumble, from
the front end, that would occur typically after 10-15 minutes of highway
driving at ~70mph. The brakes also vibrated badly when it happenned. It
occurred about a dozen times over the past 3 months, unrelated to
anything like braking, turning, changes in speed, road surface. It would
self correct if I slowed or stopped for a few minutes. I checked both
front knuckles, going so far as removing the axles to check for bearing
play, but there was none. Even when I removed this the bearing
in the hub felt a-ok. It was only when it was pressed out (and broken
into separate races and rollers) that I could see this discoloration
that indicated overheating. The races show less discoloration, hardly
detectable. The races are heatsunk to the axle and hubs so that makes
sense, that they would stay cooler.
Here is what the bearing looked like:
I dipped it in thinner and wiped it off. The brown discoloration of the rollers is in the metal, does not scrape off.
This bearing felt fine. It was impossible to diagnose; only by
disassembly (and destruction). When the axle was removed the bearing
felt completely smooth. The hubs never felt hot, or even warm, to my
hand, when I would pull off the road and check underneath when the
I guess I will go back to regarding Subaru wheel bearings as maintenance replace items, good for 75k only.
A google search of "intermittent rumble subaru" turns up a bunch of similar complaints.
This has stressed me out for a while. Glad it's fixed."
Edited by uniberp, 09 January 2015 - 04:04 AM.