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2006 Outback XT 5 speed
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Discussion Starter #1
My 2006 OBXT 5-speed manual has a pronounced vibration when accelerating. It's specifically between 20-25 MPH (can be in 2nd or 3rd gear at that speed) - the shifter visually shakes let a wet dog and there's a noticeable vibration felt in the seat. Smooths out at higher speed - unless I accelerate quickly, in which case there's a pronounced high frequency vibration (like driving over rumble strips, so a fast shaking feeling) which also shows up in the shifter and can be felt in the seat. Cruising at other speeds under light load the car feels smooth without any vibration or shaking. Definitely not a tire issue as they were recently balanced (had no effect on this) and the steering wheel doesn't shake.

The car has 86k miles. I visually inspected as much of the driveshaft and axles shafts as I could, there's nothing visually wrong other than cracking on the black coating on the center bearing isolator. The transmission mount looks fine as well - no cracks or visual damage. I suspect a bad U-joint, especially since adding weight to the car (therefore changing the U-joint angles) makes it worse. I read there's no way to check the U-joints without removing the driveshaft, and there's minimal movement when I try moving the propshaft with the car parked. Have any of you experienced and diagnosed a similar issue? Not sure what else it could be other than a U-joint problem, but with only 86k miles I wouldn't expect a U-joint failure. Thanks
 

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2009 Outback XT 5MT
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Definitely sounds like front axles to me. Has the exact symptoms on mine and after replacing them it was smooth as could be. Not sure how you can test them if they look fine.


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My 2006 OBXT 5-speed manual has a pronounced vibration when accelerating. It's specifically between 20-25 MPH (can be in 2nd or 3rd gear at that speed) - the shifter visually shakes let a wet dog and there's a noticeable vibration felt in the seat. Smooths out at higher speed - unless I accelerate quickly, in which case there's a pronounced high frequency vibration (like driving over rumble strips, so a fast shaking feeling) which also shows up in the shifter and can be felt in the seat. Cruising at other speeds under light load the car feels smooth without any vibration or shaking. Definitely not a tire issue as they were recently balanced (had no effect on this) and the steering wheel doesn't shake.



The car has 86k miles. I visually inspected as much of the driveshaft and axles shafts as I could, there's nothing visually wrong other than cracking on the black coating on the center bearing isolator. The transmission mount looks fine as well - no cracks or visual damage. I suspect a bad U-joint, especially since adding weight to the car (therefore changing the U-joint angles) makes it worse. I read there's no way to check the U-joints without removing the driveshaft, and there's minimal movement when I try moving the propshaft with the car parked. Have any of you experienced and diagnosed a similar issue? Not sure what else it could be other than a U-joint problem, but with only 86k miles I wouldn't expect a U-joint failure. Thanks
Just went through this exact same ting with the mrs outback. The rear u joint on the driveshaft went bad causing the vibrations. She had the identical symptoms and issues that your having. Tried going to a driveshaft shop to have just the u joint replaced but they would t do it. There are videos on YouTube if you feel like doing it yourself, I replaced the whole driveshaft and it fixed the issue.

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03 H6 OBW & 06 WRX Sportwagon
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if the freq. of the vibration feels about 4X the tire rotation, could be a frozen u-joint. From what I read, hard to diagnose without disconnecting the shaft.
 

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My 2006 OBXT 5-speed manual has a pronounced vibration when accelerating. It's specifically between 20-25 MPH (can be in 2nd or 3rd gear at that speed) - the shifter visually shakes let a wet dog and there's a noticeable vibration felt in the seat. Smooths out at higher speed - unless I accelerate quickly, in which case there's a pronounced high frequency vibration (like driving over rumble strips, so a fast shaking feeling) which also shows up in the shifter and can be felt in the seat. Cruising at other speeds under light load the car feels smooth without any vibration or shaking. Definitely not a tire issue as they were recently balanced (had no effect on this) and the steering wheel doesn't shake.



The car has 86k miles. I visually inspected as much of the driveshaft and axles shafts as I could, there's nothing visually wrong other than cracking on the black coating on the center bearing isolator. The transmission mount looks fine as well - no cracks or visual damage. I suspect a bad U-joint, especially since adding weight to the car (therefore changing the U-joint angles) makes it worse. I read there's no way to check the U-joints without removing the driveshaft, and there's minimal movement when I try moving the propshaft with the car parked. Have any of you experienced and diagnosed a similar issue? Not sure what else it could be other than a U-joint problem, but with only 86k miles I wouldn't expect a U-joint failure. Thanks
I'm new to this but if there is a way I think I took pics of the u joint when we replaced it I could post the pictures

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2005 Outback VDC limited 3.0r
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If you see any rust streaking from the main driveshaft u-joints then that is most likely the issue. Recently replaced my driveshaft and my old shaft the front u joint had what I thought was minor rust streaks. But was a sign of almost complete failure a week later. Literally probably one or 2 trips away from shearing.
 

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2008 Outback H6
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70 Posts
I have the same issue happening. just replaced my driveshaft (super easy job btw) and while the old one had some pretty notchy feeling U-joints, it wasn't the problem. OEM axles are headed to me right now. while under the car I checked the axles and they feel fine, but don't have the telltale green color of the OEM axles. I'm thinking OP cheaped out on some 50 dollar AutoZone replacements and now I'm paying the price.
 

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2006 Outback XT 5 speed
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Discussion Starter #8
I have the same issue happening. just replaced my driveshaft (super easy job btw) and while the old one had some pretty notchy feeling U-joints, it wasn't the problem. OEM axles are headed to me right now. while under the car I checked the axles and they feel fine, but don't have the telltale green color of the OEM axles. I'm thinking OP cheaped out on some 50 dollar AutoZone replacements and now I'm paying the price.
I think you meant original owner, not OP (original poster of this thread - me).

The history of the front axle shafts on my car is that the original right front OEM shaft inboard boot ripped open at around 50k miles and flung out the grease, and at that time I trusted my Subaru indy who works on lots of these Outbacks to install what he called a rebuilt Subaru shaft. Turns out it doesn't have the green paint and is likely not a Subaru part, but it seemed fine (it was sourced from a reputable rebuilder who does lots of these, and it was definitely not $50). Around 15k miles later, the original OEM driver side shaft boot failed, and I had a new OEM Subaru axle shaft installed at the dealer. Now 20k miles later, the car has the symptoms described above. I'd be very surprised if it's due to an axle shaft considering the shifter vibration symptom, but I'm not ruling out a (very) premature failure of the passenger side shaft (the boots still look perfect). It's much more likely a U-joint issue though - if I can measure the frequency of the vibration and it matches the driveshaft rotational frequency rather than the axle shaft (which rotates slower than the driveshaft by a factor of 4.44) I could confirm...
 

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2008 Outback H6
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hah whoops, I meant Previous Owner not OP. I've heard lots of bad things about the non OEM shafts. my car is at 100k, and it's worth it since I plan on getting another 100k out of it.
 

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Outback 2011 3.6R Premium
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I think you meant original owner, not OP (original poster of this thread - me).

The history of the front axle shafts on my car is that the original right front OEM shaft inboard boot ripped open at around 50k miles and flung out the grease, and at that time I trusted my Subaru indy who works on lots of these Outbacks to install what he called a rebuilt Subaru shaft. Turns out it doesn't have the green paint and is likely not a Subaru part, but it seemed fine (it was sourced from a reputable rebuilder who does lots of these, and it was definitely not $50). Around 15k miles later, the original OEM driver side shaft boot failed, and I had a new OEM Subaru axle shaft installed at the dealer. Now 20k miles later, the car has the symptoms described above. I'd be very surprised if it's due to an axle shaft considering the shifter vibration symptom, but I'm not ruling out a (very) premature failure of the passenger side shaft (the boots still look perfect). It's much more likely a U-joint issue though - if I can measure the frequency of the vibration and it matches the driveshaft rotational frequency rather than the axle shaft (which rotates slower than the driveshaft by a factor of 4.44) I could confirm...
If you have a non genuine driveshaft on one side I would start with replacing that as it is the most likely problem. There are many many reports of non genuine drive shafts causing the problem you are describing.

Seagrass
 

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2009 3.0R Outback
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I'll throw in another vote for driveshaft. Symptoms sound like mine before I replaced it. Under acceleration it felt like driving at high speed on extremely nobby tires or going over the "oh ****" strips on the highway.

My car had aftermarket axles installed when I bought it. The feeling from those was completely different. More a low frequency lateral "shimmy".
 

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2006 Outback XT 5 speed
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Discussion Starter #12
Update - Problem Solved. It was the aftermarket passenger side front halfshaft. I had my original driver side shaft in my garage (had ~60k miles on it), I disassembled/cleaned/regreased/rebooted it, had it installed on the passenger side. It's like a new car - no more vibration. I now know the change in feel of the car back when I had the passenger side halfshaft and front control arm bushings replaced was due to the halfshaft - it then got much worse after ~30k miles in the car.

Unfortunately I chose to replace the driveshaft first since it made more sense that a U-joint was binding. I should've done the much cheaper repair first. Anyone want to buy a perfectly good OBXT MT driveshaft with 90k miles?

I inspected the removed aftermarket halfshaft and the only difference I could find compared to OEM is that the force required to change the CVJ angle is lower. Guessing it wasn't filled with grease or the roller to cup fit is a bit too loose (or both). Either way, this is another piece of evidence that aftermarket halfshafts should NOT be used in these Subarus.
 
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