My wifes 2002 blazer 4x4 shifts in and out of 4hi "hard". Or should I say "jumps" in and out. She has the electronic 4wheel drive. When you push the 4hi button, it usually shifts into gear ok, but not always. When I shift back to 2hi, its like it "jumps" back into gear. And it don't shift right away, it usually shifts as you are deccelarating. This also occurs sometimes when shifting into 4hi, only when accelarating. 4lo works fine both ways, in and out. My understanding is the actuator motor is what makes it shift in and out of gear. This is suppose to be under the battery tray. I've taken the battery out, this looks more like a vacuum operated switch than a motor, however I did see where the cable connects to the actuator motor on the transfer case. The fact that it does shift in and out of gear, and that 4lo shifts fine, indicates to me that the motor should be ok, but not necessarily! I've also heard of a bad vacuum, or leaky vacuum, preventing it from shifting in and out of 4wheel drive. Anybody have any helpful insight on what the problem could be, and or how to troubleshoot the problem?