Car Vibrates at high speed on 2004 Subaru Forester

I just bought my Subaru 3 wks ago. It just started making a low rumbling sound and then you feel vibration all through the car. The steering wheel does not shake and it does not go away when reducing speed. It doesn't happen all the time. Mostly at high speed. It sounds like you are driving on the rumble strips along side of the road. Dealer has looked at the drive shaft and it is straight and wheels are in balance. Can you help?! DSJ

Asked by for the 2004 Subaru Forester
How about the CV joints? if one is bad, it will do this. how are the bearings? are the tires smooth?
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Yes, I had the same problem. After all the checks you mentioned plus tranny and fly wheel inspection, I had a compression test done and found cylinder 1 at only 25%. Turns out that a valve was craked.

Ask the dealer to do a compression check -- you may have a simular problem