I have a 2001 subaru outback and they replaced the the front axle. Is it normal for their to be a vibration when in drive . It runs fine it just when your at an idle when at a stop.

replace the warped disc rotors , check/ replace the front wheel bearings

to possible answers
the axles are new and the cv joints mat be firm resulting in noise transmission through failing engine mounts ( unlikely but possible )
the tread pattern may be the cause of the noise especially if the tyre pressure is incorrect
Take it back to the shop and take them for a road test to see if they can find the reason
when drive axles have to replaced , it generally means that the front lower arms have to be disconnected so a wheel alignment may also be in order

loose bolts somewhere in the front end? you have had lots of work done there. wheel weights can fall off or a rim can be difficult to balance?

I concur with anon263. When we replaced driver-side axle with an aftermarket one, the vibration was horrible. Most people around me would not believe that was the cause, but as soon as we replaced it with a Subaru OEM rebuilt axle, the vibration disappeared. Get a new one from Subaru if you can afford it. Here's hoping the rebuilt one will last, although some out there have said that it may cause other problems down the line, most likely just because it won't last as long as a new one. The aftermarket axles, with exception of MW, are off just enough in their designs and spline size to allow harmonic vibration to transfer from the engine to the wheel and then your steering wheel when you are stopped at a stop sign and still in gear. The vibration usually goes away when you put it in neutral or park. In my case, I even thought I detected some strange vibration when driving.

Replace the c.v boots or will damage you c.v joint's then you will need to replace the hole shaft, if you going to get it done at a repair shop you be looking about $250.00 to $300.00 both side's, if your going to do it you self parts run about $20.00 to $30.00 each.

need to have front tires rebalanced

If I understand you correctly, you feel a vibration it the brake pedal when you apply the brakes. Is that correct?
Have your brake rotors re surfaced; they are warped.

"engine makes cavitating noise" ....what does this mean?

i would have your oil filter changed with oil filter, air filter, replace spark plugs, have all your fluids checked( front and rear diff, tranny fluid, coolant, ) normally if you go to a shop they will have package systems with all or most of these items. if i were you i'd call around and see which shop around you has the best deals

I would first check and see if you have a build up of off ice on the inside of the wheels. If this started all of a sudden it might also be a brake problem like I have run into in the last few weeks of bad weather. The duel caliper brakes had one caliper piston stick and let the brake pad be uneven causing a vibration in the front end. Sometimes it would release and work fine. Hope its the ice in your wheels, but if not I would take a look at brakes before spending a lot of money. Good luck and have a good day.

Did you recently replace the axles on the vehicle? This problem commonly occurs in Subarus when you replace the axles with non-OEM parts. The only fix seems to be to swap out the axles for OEM parts. Search the forums at subaruoutback.org for many stories of the same condition and some theories on why non-OEM axles cause the problem.