Hi, I have a 99 Blazer LT with 4x4 issues. When I first start the car up I am able to push 4hi and it will engauge with no problems, but after I drive down the road about a mile or above 15mph the 4 wheel drive will not respond at all. At that point I can pull over on the road and turn the car off and start it back up and BAM the 4 wheel drive will work again. At least untill I go about 100 feet or 15mph. Can someone please tell me you have had this issue and tell me how to fix it....