My front end started whining two days ago from.

My front end started whining two days ago from what seems like the front passenger side, not a whine like youd typically get with a thrown bearing but more like the sound of a roulette wheel. I Took the wheel, hub, rotor and cv shaft out, all of which seem to be an excellent condition then t occured to me that it MAY be that yhe four wheel drive wont disengage completely. This sound occurs in 2 wheel drive only, once 4 wheel drive is engaged the noise ceases. Since the sound began it will not go into 4 hi, only 4 lo. Am I right assuming that the 4x4 cyllanoid or actuator may be the problem? Your help is much needed!