CV axle's are mainly inspected for excessive play forward and backward's but normally a test drive into a large parking lot where you turn the steering wheel hard to the left and accelerate hard and then the same to the right. If you hear a loud popping sound you've found the problem.
I would guess you don't have a CV axle problem from your description, it sound's a lot more like at least one broken motor mount under the engine. They can be checked by having someone watch the engine bay as you hold the brake hard, place the car in drive and again accelerate with a quick jab to 2500 rpm on the gas petal. Then do the same with Rev and you'll see the engine raise up several inch's showing you that lower mount is broken. The vibration comes in at road speed when the engine is running at coast speed. Meaning 35 to 50 MPH when the engine rev's have caught up with the transfer of power to the drive wheel's so you no longer have to accelerate or let of the gas. When in the coast part of the drive cycle power in slightly added by the engine causing torque to lift and drop the engine rapidly. Letting off the gas or accelerating will cause the vibration to stop. Happy Motoring. Tim
