Hi all I have a Ford 9" Big bering axle and have 4.56 gears hooked up to a dana 20 and np435. Ive noticed that my Yukon Grizzly locker (only has 5k miles on it) has been popping more frequently on all sorts of terrain from asphalt to dirt roads to sand. It doesn't matter if I'm turning or not but when it pops it is loud and shakes the whole bronco. Also my gear oil in the rear appears to be metallic in color even after i have done several gear oil changes on the diff. Any ideas on what could be causing this?