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Discussion Starter · #1 · (Edited)
2014 2.5 manual transmission.

The issue is getting worse. I notice it about 70mph and it gets really bad at 80mph. The entire car shudders but not continually.

For example, it'll shudder in a cycle. Like shutter for one second then stop for one second. Or shutter three times within 2 seconds and then stop for half a second.

I have tried taking the transmission out of gear, accelerating vs coasting but neither made a change.

I assumed the issue was CV axles. The front suspension makes a popping noise at full turn and slow speed sometimes, only recently. Confusingly, the CV boots are fine.

I have read through threads with similar titles on here. I doubt the transmission is the issue given my test, same with engine. Any ideas?
 

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2010 2.5 CVT Limited
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The 6MT cars eventually experience problems with the viscous center differential but that usually manifests at low speed, tight turns.

Any other conditions that can be related to when this happens?
Car cold vs warmed up
Turning in either direction
A/C on or off

I don't think I've read of a problem like this posted before.
 

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Discussion Starter · #4 ·
The car is always warmed up for me to be able to get up to 70 something miles per hour. I can try with the AC off later. The issue happens when I am driving straight and I'm not usually turning very much at 80 mph.

I tested out the popping in an empty parking lot just now. And of course maybe these are two separate issues. I don't know.

It does pop occasionally but I realized that when I focused on the sound and feel, there's more happening than just the occasional pop. It has more subtle thud sounds and sometimes it feels like the front end is slipping in the opposite direction of the turn. Happens in both directions.

It's like a subtler version of what happens when you lock a truck in four wheel drive and turn as hard as you can in a parking lot.
 

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Outback 2011 3.6R Premium (sold Jan 22)
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I am wondering if it is the drive shaft from the gearbox to the rear diff. If it is this, it could be the centre carrier bearing.

Seagrass
 
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2012 OB , 2017 Impreza
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The issue is getting worse. I notice it about 70mph and it gets really bad at 80mph. The entire car shudders but not continually.
Classic dragging brakes..... the faster you go, the more heat is generated, the more it drags. Rotor begins to warp and you feel it.

Slowing down and driving 40MPH may allow rotor to cool enough for the vibration to cease.

How to test for dragging brakes:
  1. Drive car at highway speeds for at least 20 minutes.
  2. Come to stop trying to use the brakes as little as possible.
  3. GENTLY feel the lugnuts with your fingers.
  4. If any wheel is hotter than others, there is your dragging brakes.
WARNING: The lugnuts can get hot enough to burn your fingers.

Also: Prolonged driving with dragging brakes WILL damage wheel-bearings. The bearings may not fail today... but within a year, they will get noisy due to the grease being boiled out them.
 

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2012 Legacy 2.5GT-L
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So just dealt with what sounds like a similar issue on my 12 LGT - it would shudder on acceleration (even light acceleration) but only at highway speeds (70+) as well as, in my case, when doing any sort of right turn, but again only at highway speeds (so changing lanes, sweeping right corners, etc. - basically as soon as you started applying pressure on the steering wheel) - pretty typical for a bad cv joint, but all 4 axles looked just fine - started checking wheel bearings and had significant motion rocking the drivers front wheel, so thought great - wheel bearing time - looked more carefully since more than just the wheel was moving when I rocked it and it turned out to be the front bushing on the lower control arm was completely fried. Replaced both lower control arms (since they come with the front/rear bushings and the ball joint, and are reasonably inexpensive - I went OEM at 118 each) - the bushing was so destroyed I could just push the inner sleeve all the way out! Anyway - new parts are in, and everything is fine now! (I actually had a clunk I would hear when backing out of the driveway that I assumed was the a-pillar issue that has a tsb for a popping sound - turns out it was the bushing, too - it's gone now)
 
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