My 97 Blazer is trying to Engage 4x4 when i accelerate really hard, or when im going down a highway at about 65-75 mph. It's not all the time, but when it happens, i have to pull over, Press my 4x4 button, let it fully engage, and then take it back out, then all is fine. it a loud grinding sound, seaming like it's coming from the pass. side front wheel. WTH could this be??? Any Suggestions?