When I'm in deep snow and need 4 wheel drive I put it in neutral and shift to 4 Lo. I can hear it shift and can feel it is in a low gear ratio, but when I put it in drive I am instantly stuck and can only see one wheel spin. The same with 4 Hi. Now, if I put it in AWD I can drive right out of the deepest snow. I can see all four wheels turning. Does anyone know if this is a common problem with envoys? Is there something I can check like an actuator? I have an 03 envoy sle 4.2L 4x4.