Vibration when turning into corners

I have this vibration issue with my Subaru that I can’t seem to figure out. It’s an Outback 3.0 from 2005

When turning into a corner there is a certain point when turning the steering wheel at which I feel a small thud and then a vibration sets in.
The angle of the steering wheel is somewhere between 30 and 40 degrees.
The vibration can been felt in the steering wheel and also in the seats.
As soon as the car is driving in a straight line again the vibration is gone.
This happens at a speed of about 60kph and up.
If I keep the steering wheel just before this point there is no vibration and at lower speeds it’s not there either.

The vibration can also be induced by suddenly releasing the throttle in a corner.

If I apply the brakes while the car is vibrating it stops and comes back again when releasing the brakes.
If I apply throttle while the car is vibrating the vibration gets less, not completely gone.
The vibration is best felt when coasting through the corner.

I’ve replaced some parts which made it better, but non fixed the issue.
Kinda running out of ideas.
Anyone have an idea on what to check next?

Parts that have been replaced:
Steering rack (with rods)
Front wheel bearings
Front suspension bushings
Brake disks and pads (front + back)
Transmission mount
Rear differential mount bushings
Propshaft u joints + rebalancing
Front wheels balanced
Switch wheels front to back (no difference)

My first hunch is CV joints. Any knocking/crackling sounds when accelerating while in a sharp turn?

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There is no knocking/crackling sound, just the vibration. Which is the same for left and right turns.

I did try a set of aftermarket driveshafts (SKF), which did not help. They induced even more vibrations while driving straight, so I replaced the original

In addition to the CV joints, I have to wonder about the Center Viscous Coupler.

Have you ever run the car for more than… let’s say… 100 miles with the temporary spare mounted?
Have you failed to rotate the tires on a consistent basis (every 5k or 7.5k miles)?
Are any of the tires not matched to the others in terms of tread depth or size?

If the answer to any of those questions is “yes”, then a failing Center Viscous Coupler could be the culprit.

I have driven about 2k miles right now.
The spare wheel looks brand new.
I don’t know if the previous owner switched front to back.
All tires are the same brand and the profile is about the same.

I have a 5 speed automatic transmission.
Don’t think they have the center viscous coupler but uses multi transfer plates.

Is there a way to check that it is this part that’s failing?

Did you check to see if tread depths match?

They all look quite similar, will do a measurement tomorrow

check to see if your caliper bolts are loose. it seems to go away when pressing the brakes. the caliper can be shifting causing the thud and when you have the brakes on its putting tension stopping the vibration

Caliper bolts are tight, checked everything twice to be sure.

I measured tire profile: FL 5,3mm FR 5,0mm RL 6mm RR 5,3mm
Largest difference in profile depth is 1mm between front right and rear left.

I noticed that the vibration can also be induced at low speeds when in a corner and suddenly releasing throttle.

I don’t notice any binding at low speeds, there is no tire hopping on tight corners.
It does feel that the vibration is coming from the end of the transmission that it’s introducing some kind of unbalance which makes the propshaft hop or something.
Could the vibration be comming from a bad center diff bearing or something like that?
I do hear a slight whining noice when driving, but the exhaust is masking the sound a bit

just out of curiosity did you check to see if a motor mount is bad? you have changed tranny mount and diff mount.

I used to have 2003 Outback, I believe the same generation as yours, although it was 5-speed stick-shift.

I did not have vibration you describe, but had that “kicks” in transmission, between front and rear as I was letting the gas go on the certain speeds.
Long story short - it was an excessive lag in the central differential gears, and once I adjusted that to be in spec - that “kicks” went away.

Another Subaru I used to have was 1996 Legacy wagon and it had a whining sound under moderate load at certain speeds. That went away after replacing differentials fluid in both central and rear diffs.
That Legacy was purchased very cheap and had all 4 wheels of different brands and sizes, yet I [stupidly] drove it for ~1000 miles more before I replaced them… viscous coupler survived that abuse just fine, so I would keep that part relatively low on suspect list.

Pay attention that front diff fluid is easy to check with a small dip-stick on the passenger side, very next to the firewall.

If you Subie has unknown previous maintenance records or you did not replace diff fluids at 60K schedule (my recollection from memory) - I would entertain that idea.

Subaru uses different types of center drive couplings on auto and manual transmission cars, so experience with one can’t automatically be assumed to translate to another. They’ve also varied the coupling designs over the years.

that’s quite right

in addition, around 2010 for the central drive coupling they had different types between “base” trim and “advanced” trims, where manual and base-trim automatic shared viscous one, while other trims received electronically-controlled clutch type

after owning 6 Subarus in the past, it’s not my “love” anymore, so I do not monitor the latest generations internals

Motor mounts feel fine, no play and when shaking the engine the entire car shakes as well.

I’ve already replaced the diff oil, front and back.
The transmission was flushed 6k miles ago.

I did check the play on the propshaft connections.
The connection to the diff feels fine.
The side on the transmission has play in all directions. Made a video to show this.
You can hear it as well.
Looks to me that this play should not be there, because the propshaft is completely balanced
and it looks weird to me that the connection can move.

I do not know if this much of “play” is too much, but I would bet that some should be present as this part is supposed to move

it could be an option to find a similar aged Outback on used cars lot and compare

in addition I would suggest to get one front wheel raised and see how much play wheel would have rotating forward/backward - it would give an idea how much play differential has

in my case it was visually way too much, so when I measured play in the final drive gear through the oil drain plug port - it only confirmed what I found with a raised wheel inspection

With front wheels of the ground there is not much play.

The propshaft has play in length direction, but I would expect up down left and right to be tight.
Can’t imagine that it should be possible to move it in those directions since the shaft that it’s on is kept in place by ball bearings

time for “mystery mid-2000 Subaru shopper trip to the nearby used cars lot” ? :slight_smile:

I checked two 4eat’s and they also have some play there. Less than mine, so don’t know if that could cause vibration.

Did do an extra check of the motor mounts.
They seem solid with some small crack on it.
When applying a pry bar I can move the engine and kinda induce a vibration which makes the transmission move sideways.
When applying throttle the engine moves a little.
But when I suddenly release it the engine moves the other way and gives a shake to the entire chassis.
Could it be that the mounts have gotten too soft and not functioning correctly?