About a month ago my 4x4 quit working. I checked the 25A fuse and it was not blown. I am able to put it into 4-LOW, and the transfer case engages -- as my rear wheels are running in low gear. I suspected the 4WD actuator to be the culprit, it is the 2-pin thermal style. I changed that out today, and my 4WD still doesn't engage. I'm seeking advice and suggestions as where to look next.