I have a 2013 FX4 Screw, 2" Zone leveling kit running 275/70 18 Coopers M&s'S on stock rims. I was wondering if anyone has had my problem, which is in two wheel drive when the tires break loose on the snow I hear a chatter from the front diff, it sounds like the it is not fully disengaed from 4x4. I have checked for tire rub, no evidence of that. I have the warranty and an appt. but, would like to be able to rebut the service dept. if they say its normal? Any thoughts would be appreciated. Thanks from Alaska.