2002 Dodge Dakota 4 wheel drive indication

I accidently left my dakota in 4H and got on the freeway - up to 70 mph. About 400 miles later I noticed the 4H light blinking. When selected to 2 wheel drive there is no noise and no light. When selected to 4L I can hear a noise and the light is lit. When selected to 4H there is no noise, the light blinks a couple of times and goes out. What pray tell have I messed up. Thanks