uniberp1

When it happens, it gets harsher when I touch the brakes, which indicates a wheel bearing. When it resets, no change when braking. Harshness is just in increase in audible throughout the car. Maybe the steering wheel. Here's what I suspect. This car has 16" wide flat-profile tires. (Yokohama Avid Ascend)The additional leverage put on the wheel bearing due to the large effective offset increases the pressure on the bearing and heat distorts it. The 99 has taller narrow 15 tires. I've had 3 wheel bearing replacements in this car. Granted one might have been cheap, but the other 2 were an NTN and the SKF hub kit. 140k miles. Maybe pothole Michigan has something to do with it. Eventually I will get tired of dealing with it, even intermittantly, and replace one of the bearings. I run it on stands and listen to identify the weaker bearing.

Driveshaft?

2008 Forester NA. Iintermittant wheel or driveline vibration, seems to be up front. I've previously replaced front wheel bearings/seals. Swapped axles around. One new axle at some point. Seems to heat up randomly on highway and start grinding faintly, increasing, until speed changes. It used to alarm me. Now I just slow down and find a speed where the noise remains constant, not getting louder or changing. After stopping it seems to cool down and reset. Every few days it happens. I think I know why it happens on this year and model and not on my 1999 ForesterNA.

Subarus require spark plug replacement every 40k miles or so. You might check those.

They may rub on the chassis when turning. Seems like stock size tires com pretty close as it is.

You should be able to grip the strut shaft with a vice grip and loosen the nut. The old strut is trash anyhow.

I don't see alignment listed anywhere in this thread. Mis-alignment can amplify any minor play to completely out of spec.

It's all in how the car was treated and maintained and you have no way of knowing that. The engines have aluminum blocks and heads, and even though they now have timing chain instead of belts, they still expand and contract with heat, and that can loosen them up. The high-performance ones are like all high performance cars, designed for thrills and who cares if they last. You can't have everything. I like mine because I know them and can maintain and repair them, but it took me 3 engine/tranny installs (and numerous bearing, axle, struts) to learn those lessons.

I like the Yoko Avid Ascents on my 08 Forester. Apparently they are made with "orange oil" which is supposedly more temp stable. I have a Discount all season "Arizonan" all season house brand on the 99 Forester. They are ok, but a little louder on the pavement.

I was thinking it might be an ideal setup for a t-top conversion, although I don't know why I would want to. There's already no door frame, just reinforce the roof span and create some kind of seal gutter for the panels. I've got an extra 1999 Forester that would be good for going to the beach.

Yes, the whole point of a K&N is to let little rocks in so they swirl in the vortex and clean the intake walls. Cleaning it just removes some of those helpful little rocks.

If the vibration is constant and predictable, it's a tire, wheel, wheel bearing or axle. My favorite source of intermittant vibration is when a caliper drags just enough to heat up the wheel bearing and expands it to the point that it loosens just enough to vibrate. I have to exit the expressway and drive around slowly for a couple minutes until it cools off. Of course now 1 year after I replaced the caliper, with no occurrences since, it's starting to do it again... I think. Then again the left side VVT pressure sensor started leaking oil and threw P0028 codes. That seemed to cause some rough running a couple times.

IMO the best thing you can do use a remote starter and let it warm up before you drive it.

Or it stops working completely because the motor is overheating. Overheating can also cause excesses current draw, hence the stop action. Clean up the motor, if possible.

Frozen balljoints can make steering heavy, but I've never seen frozen ones on a subaru, only super loose ones.