Forester--vibration at higher speeds

[ThosL]

I have a 2002 Forester, 250K miles.  I was trying to diagnose my Forester with a mechanically inclined friend.  Over 55 especially and going uphill with foot on the pedal the vibration is the worst.  A mechanic friend of Sam thought either it would likely be tire balancing or axles.   I had the tires recently rotated so don't think it is them.  Any direction on trying to figure this out would be appreciated.  I had alignment done after replacing a tie rod end so think the front end is ok.

[ocei77]

Get the front end off the ground and holding at the sides, then on the verticals, see if you have play.

Check the ball joints by prying between the A arm and the knuckle.

Make sure all your lug nuts are tight.

Double check the axle nut.

O.

[forester2002s]

Could also be the rear driveshaft, especially if you get a vibration under load.

[montana tom]

Rear driveline, usually at the u-joint directly behind the transmission.

CV axels can do this as well. 

[ThosL]

As others said it could be the driveshaft.  My guess is possibly the tires that have under 10k in life left.  I replaced one of the front wheel knuckles with a junkyard one. I had one stud on that wheel which was stripped so had 4/5 good studs, not sure if that could have distorted something.   

Friend's mechanic said to drive it slow in a tight circle for "clicking" tied to CV axles.  Also that the tie rods, ball joints, bearings etc. if they are not 100% would account for the vibration.

Edited September 4, 2023 by ThosL

[el_freddo]

The “extreme” end of the spectrum for the cause of this vibration is a worn rear diff. 

It could also be the centre bearing in the tailshaft.

Cheers 

Bennie