i currently have a 2002 trailblazer

1st
when i place my truck in 4 high i get a grinding noise from the front end when im driving and the push button light flashes trying to figure out the problem when i place it in 4 low no noise but the light is flashing and when in 2 hi no flashing light and no noise.

2nd
when i use the heater or ac i have coolant vapor or smell coming through the vents just wondering if the heater core is bad or what also no coolant on the floor inside the truck

please help lost and need soe answer before i repair