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.

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.

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

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

CV axels can do this as well. 

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, 20232 yr by ThosL

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