i have a 1997 blazer ,that is not going into 4hi or lo.the push button tells me that it is but not. front wheels dont spin. . i stopped at a chevy garage and ask them what would cause this ,.they told mr that the two main cause was the decoder on the transaxle or ht e box on the pass firewall. when i ask them if the front drive shaft turns all the time they told me that it only turns in 4hi or lo ,if it doesnt htat it would be those two items . if it does then it is your actuator or in side the front axle not engaging. well too say when i put it in 4 hi tonight the front drive sahft turns.i alsop put it in 4hi and check vacuum at the actuator and i have vacuum.i heard of that there is a rod or something that gets hung up.my fatherin law had the same problem he said that the garage just tapped on that rod and it work. i am not sure what rod he was talking about. if i would unhoook the cable at the actuator can you pull on that cable manually to see if goes in that way. how does the cable unhook from the front axle?please help.

 

the cable going from the actuator underneath your battery tray gets vacuum and pulls the cable engaging your front axle. I had the same problem, it ended up being a hole in the vacuum line and a rip in the actuator. Your cable could be frozen try taking it out of the actuator (there is a spring clip that you undo to get the cable out) and pulling on it. If you pull on the cable and get no play then its frozen. Use your hands pilers or vise grips to pull it