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Vibration at speeds of 40-50MPH


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Hi,

I have a 1998 subaru outback legacy Standard transmission with 138K miles, that I am experiencing vibration problems with.

 

It occurs at 40-50mph and is a loud low noise, like the opening a window at highway speeds. It is most felt in the seat of the car which makes me believe it has to be from the back as the steering wheel does not vibrate. I don't believe it is the tranny because i can't feel the gear shift vibrate. It does not vibrate until that certain speed. It seems to go away with speeds past 55mph. It is not the tires as I have had them done, along with a wheel alignment. During the summer I can barely notice this vibration, although it is still there. It is the worst in -4 degree whether and as the car warms up it seems to not vibrate as much.

 

I hope you can give me some advice, I have already read about wheel bearings, drive shaft issues, tranny issues, but i can't quite pin point it.

 

Thanks very much!

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there are any number of things that can cause a vibration like you describe.

 

wheel bearings - altho those tend to make noise at all speeds - but doesnt rule them out either...

 

bad axle

 

bad driveshaft center bearing

 

bad U-joints

 

bad struts

 

various bushings gone bad...

 

from your description I think i would carefully inspect the driveshaft components first.

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Hi,

I have a 1998 subaru outback legacy Standard transmission with 138K miles, that I am experiencing vibration problems with.

 

It occurs at 40-50mph and is a loud low noise, like the opening a window at highway speeds.

 

I've had many Subarus develop symtoms like that. With mine it was usually the universal joints in the rear driveshaft. Easy fix IF you can get replacement joints. Not always easy to find. Subaru will tell you they are not replacable and sell you a whole new driveshaft. Not true. I've replaced many but it's a little trick getting them apart since they're staked in. My comments are for the 80s-90s rigs. Can't say on the newer ones.

 

By the way, I've also had similar noises when rear wheel bearings went out on the late 90s and newer Subarus. NEVER had one go bad on the older rigs.

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have a coupla buddies pace you on the road and observe all 4 wheels for bouncing (bad strut/shock or tire) and 'run-out'/wobbling.

 

If nothing odd is seen, probably the driveshaft or ???

 

I never did win an argument with DiscountTire about a vibration with a bad tire. Then, it started showing it's steel belt after only being 2/3rd worn out. Glad I complained twice because they knocked off $$ on my next set of 4. However, that vibration did change when the tires were rotated, definitely felt in the steering wheel too.

 

At that mileage/age, if you are on original shocks/struts - they are likely shot. That's about 10K miles or less per year. That usually means a lot of secondary roads and stop-go type driving. Rough on suspension/drivetrain parts.

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Thanks for all the tips!

I decided to rotate the tires and yet it was still a vibration in the rear. I believe that it may be the drive shaft because I did do the clutch myself a year ago and had to remove it. I may have knocked off a weight or misaligned it, although i made sure i replaced it in the same way it was taken out. I am thinking it will have to go to a mechanic for a sure test because of what I am limited to being able to do.

 

Thanks again for the tips, at least now I have some ideas to base my problem off of.

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There are no weights to knock off. Did you notice a vibration starting at a higher speed, very subtle, then slowly happnening sooner and getting worse?

 

It really sounds like a bad universal joint, time to drop the driveshaft and inspect the joints, otherwise we go look at tires again.

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There are no weights to knock off.

 

Yes, there are steel weights that are tack-welded on. I've knocked off a few rusty ones that were pretty much gone anyway.

 

Driveshaft is easy to check. Just unhook one end and wobble it all directions. If stiff - or loose - in needs new joints.

 

I suspect most repair shops would refuse to install new joints. I know my local Subaru dealer won't. That's why I do my own.

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  • 3 years later...

Believe it or not I am still having this issue, I haven't been able to figure it out 4 years later. But tonight I went under the car again and took a look at the driveshaft and next to the center bearing was what looked like old old grease. Then another u-joint had mine spots of old old grease and considering that these are supposed to be sealed I would say that they have gone bad. Any thoughts?

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1st step swap tires f-r on one side then the other and see if it moves. If it doesnt odds are its the driveshaft. Its a bit early for a bad universal joint mileage wise but not age wise. 

 

These are sealed uiniversals so it might behoove you to get more agresive in diagnoses as the failure can be hideous. 

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