Is replacing CV boots one of those things that if you replace the two outter ones that you have to replace the two inner ones or can you just replace the two outter ones and not the two inner ones?

 

You can only replace the outers if you want. If the inners have the same mileage as the outers you might as well replace the whole axle - cost is about the same as boots & much easier.

Also if you hear any clicking you want to replace the axle.

 

What causes the clicking sound exactly...? I think I heard some clicking noises sometimes when I back up and change gear to go forward and I think when I accelerate away from stop sign sometimes(I have an auto)... But most of the times the music is turn up too loud to hear anything at all...

 

Just replace the outer ones, and don't worry about the inside ones... they very seldomly go bad. Just do the outers, and your good to go.