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Searching for driveline vibration, feeling defeated.


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Back in June I picked up an outback XT with 175k miles, that had a blown turbo and motor. Over the summer a friend and I put in a new short block, VF52, rebuilt heads, a tune from EFI, and everything needed to get the car running nicely, which it does. I also swapped in LGT brakes, and put in new shocks/springs among many other things. Its come a long way and I'm proud of the progress I've made. However, I've been chasing what feels like moderate drivetrain vibration. Its most noticeable under boost or heavy load in higher gears, nonexistant when just putting around.

 

So far I've swapped in a SMF/clutch kit (it needed a new clutch anyway) which did not help. While doing so I noticed the driveshaft ujoints were in terrible shape, so I put in a new driveshaft, which did not help.

 

The car does need a rear wheel bearing, as well as the bearings in the transfer case as they are just starting to wine, but I don't think either of those would cause the the vibration. I do have group N motor mounts/trans mount but from what I've read the NHV levels didn't change much over stock mounts.

 

Need your suggestions. What else could cause this? The only things I can think of are an axle, an issue with the trans or rear dif, dif mounts, or maybe its the tune? I'll probably schedule some diag time at EFI but would love some ideas in the mean time. Thanks everyone

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Does the vibration eminate from transmission tunnel or from the rear if that makes sense? The Group N mounts transmitt more driveline feedback so they may be exposing a problem within the gearbox maybe a bad bearing on the tailshaft or perhaps an out of balance axle.

 

Are you sure all four wheels are true?

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It feels like its coming from the front/middle of the car. I think the wheels are slightly out of balance, I get a little bit of a shake at the wheel over 70 but the issue I'm referring to is only under hard load/boost. Its completely dependant on how much how much load the car is under, not on speed/rpm.

 

The gearbox shifts fine but like I mentioned the transfer case is starting to make some noise. That might be my next repair attempt, for no other reason to rule it out and fix the bearing noise at the same time.

 

Any way to test for an out of balance axle?

 

Appreciate the feedback!

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Seems like your front diff is the epicenter of the vibrations. The axlewould need to be tested on a lift, in gear to inspect visually but that probably isnt the issue.

 

What color is the transmission case specifically the area arounf the front differential? Any discoloration? Dark color no associated with fluid/dust/grime?

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The transmission case doesn't look like anything out of the ordinary for one with 178k miles. Its kind of dark/dirty but I don't see any obvious signs of leaks. Guess I mine as well replace the bearings in the dif and see if that helps. What's a couple hundred more dollars?! :)
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sorry, do you mean front dif or the center dif/transfer case? If it actually is the front dif than I'd just have to get a new transmission. If its the bearings inside the center dif/transfer case than those I could replace.
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The stiffer mounts will increase NHV, my wagon is noisy, and will vibrate when I roll into the throttle. If I downshift and go WOT I don't feel it, but other things are happening much faster so my mind is focused other places.

 

Yes the bearings can be replaced, I think there is a DIY or sticky here about it.

 

I know a tranny guy too, in Windsor Locks. If you can get him the tranny...

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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The stiffer mounts will increase NHV, my wagon is noisy, and will vibrate when I roll into the throttle. If I downshift and go WOT I don't feel it, but other things are happening much faster so my mind is focused other places.

 

Yes the bearings can be replaced, I think there is a DIY or sticky here about it.

 

I know a tranny guy too, in Windsor Locks. If you can get him the tranny...

 

Thank you. It may very well just be the mounts. Whatever it is, it drive me nutes. I like a smooth and refined ride. Guess I bought the wrong car!

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I have LWFW, polly read diff cradle bushings, STi tranny mount, Moore Blast Plates, Koni's set towards firm, AVO chassis braces, you want to talk about noise... car runs great.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Try looking here for ideas. Most of the time, it's actually wheel balance or bent/out of round wheels.

 

http://legacygt.com/forums/showthread.php/soooo-many-vibration-threads-217316.html?t=217316

 

Great info in that thread, thanks! I know I need a rear wheel bearing, so I'll do that first. If it ever snows I'll throw my snow tires/wheels on to see if that rules out my summers.

 

If its not the wheel bearing or tires, I'm leaning towards an axle issue. I did reboot to two front inner boots, but unfortunately was unable to keep the orientation of the three rollers on the shaft the same. Tried my best but they found a way to fall off. I do plan to have EFI to some diag work and I'm sure they'd be able to spot an out of balance axle with it running on a lift.

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