It's not the actuator, you said the driveshaft was spinning. Your problem is somewhere between the pinion on the front axle and the hubs, my guess is the hubs or cams. Just remember that the guy at the parts store has no idea what is wrong with your truck since he has not looked at it. I am too lazy to read back through the whole thread so I'm not sure if the 4x4 has ever worked since you've owned it so I don't know you may have a broken axle shaft. The hubs engage when the axles spin so all it takes to lose 4x4 is one bad hub. Jack up the front with the hubs on, leave the wheels on so the hubs are not going to walk out on you, one side at a time spin the axle shaft at the joints to see if the hubs engage. Spinning the tire will do nothing you have to spin the axle. If one side doesn't engage that is obviously where your problem is which could be a bad hub or one that needs cleaned or a bad cam. If both sides engage individually then your problem is either a snapped axle, pinion, ring gear or spider gears. To learn more about the hubs just do a search and you'll find alot of info with pictures and step by step instructions, or maybe you're over your head but either way good luck and don't go wasting money on parts until you find the culprit or you'll be like so many others that end up selling their rigs because they're tired of spending money on it when proper diagnosis would have saved them hundreds or more.
