Emarine88

Hello, i have a 96 jeep cherokee. I've been hearing this noise for about 2 months now and its driving me crazy! It's not a constant noise, it goes and comes. You mainly hear it when you're going up a hill, turning, or in idle. You'll never hear the noise when you?re driving at a constant speed. My mechanic said the sound is coming from the transfer case. the noise sounds like a vibrating noise, almost as if something is being banged with something else. he mentioned that it could be that i might have to change the fluid or that something might be broken inside the case. Now i'm no mechanic, nor do i do any type of work on my car. How much am i looking to spend. Also, can anyone guess what this noise is/what i can do to fix it? How serious is this? i've been driving it like this for a while now and i haven't noticed any serious damage. Any input would be great appreciated. Thanks!