'06 6-cyl has strange rear-end fishtailing issue

[carve]

My friend has an '06 6-cyl Outback. In the snow, the rear end will gently step out one side, he'll correct, and it'll gently drift to the other side, and so on. It does this even when maintaining a steady pace. I thought he might have limited slip locking up, but since it happens when maintaing speed that probably isn't it.

It has M+S rated all-season pirelli tires (they look surprisingly "street" to have the M+S rating, but they're fairly new and rotated regularly)

Any ideas what could be causing this handling weirdness?

[Banana]

Well, I dont know about snow, but if it happens on ice its called "ghost-walking". If I understand the issue correctly, a load in the rear of the car changes the allignment, which causes this.

Use the search function, and you should find a few threads on it.

[carve]

Thanks. I found lots of people complaining about it, but not much in the way of a fix. Is it just something people live with, like the steering wheel shimmy?

[jeramifrost]

I would be leery of the tires. I drive an 08 and haven't had any problems with proper tires. Under normal conditions there is 55% power to the rear so it could have a light tendency to act like a RWD especially if the tires are not adequate for the conditions. What tires do you have on there out of curiosity?

[rockhopjohn]

Originally Posted by carve

Thanks. I found lots of people complaining about it, but not much in the way of a fix. Is it just something people live with, like the steering wheel shimmy?

Best fix to date seems to be to get goo snow tires, and have the car realigned with about 200 lbs of weight in the back, since it usually happens when the cars are moderately to heavily loaded.

[arthuruscg]

I would recommend getting Whileline's KCA 399 rear camber kit when getting your alignment and take it to a shop that is more performance orientated or you know the alignment tech. You want to have 0 toe and 0 to -1 camber in the rear.
From the factory the rear toe adjuster will slightly change the rear camber and does not have enough adjustment to have matching specs in the rear.

I noticed a big difference after my alignment, even going over expansion joins the suspension cycles evenly, with no weird side shimmy.

[Somerset Max]

If the car has a Limited Slip rear differential, I would be very suspicious of the LS diff. These devices are great at low speed in the winter, but at highway speeds, on a slippery surface, they can cause the type of problem that was described.