How do we correct a vibration when car is in gear between 32 and 40 m on 2001 Subaru Outback

The problem occurs all the time between 32 and 40 mph. Particularly noticeable on freshly paved roads. Just replaced right front axle, fixed heat shield on exhaust and replaced disc pads on front brakes and resurfaced rotors. Tires realigned and balanced. Mechanic thought new axle was defective and put in another one. Same noise/vibration exists. It only occurs when accelerating--doesn't happen in neutral or coasting downhill. Ideas?

by in Oklahoma City, OK on April 16, 2013
3 answers 4 comments
ANSWER by on April 16, 2013
is this all wheel drive? if so poss u joints in rear drive shaft
COMMENT by on April 16, 2013
It is all-wheel drive. I will mention this possibility to my mechanic. Thank you.
ANSWER by on April 16, 2013
How about the left front axle? Sounds like an inner axle tripod. (cv-joint) more like a shake instead of a vibe would be the result. Only when accelerating, let off get smooth, push gas pedal again, shake again, sound like your trouble?
COMMENT by on April 16, 2013
It seems more like a noise than a shake or vibe. Steering wheel is steady with no vibe. You are right about only when accelerating. I will pass your idea to my mechanic. Thanks so much.
COMMENT by on April 16, 2013
As greg suggested could be in the rear shaft, have mechanic remove it and test drive!
COMMENT by on April 16, 2013
Thanks for the advice. I will pass along to the mechanic.
ANSWER by on April 16, 2013
sounds like wheel bearings to me. as it gets worse you will notice sound increase and vibration increase. jack the ride up and check for play in the tire. will also notice excessive wear to brake pads(black dust on rim). check all tires.