2006 Honda CRV Noise when hard turns are made!

Just recently noticed a "moan" type sound when I either turn into a parking space or make a u-turn. Can either be making a right or left turn and hear this noise. When I had my oil changed recently, I asked the mechanic to please check it out and he said the noise appears to be coming from the "rear and sounds like the gears are binding". He does not make this repair. It is Real time 4 wheel drive. Am I doing more damage by driving it? And it sounds like this could be a costly repair? Any suggestions would be incredibly helpful! Thanks you.