Check to see if the breather hose is still in the upward position. The clip on the end of mine broke, so the breather was laying flat on top of the axle housing, rain water got in. When I applied power to the diff lock, it progressively got slower, then wouldn't lock anymore. I pulled it apart, regreased it like others recommended, but it still didn't work. My guess is the motor fried. Toyota only stocks the actuator assembly...$520 or so on discount!! Right now, I'm locker-less....can't afford to spend that kind of money. At least it's in the unlocked position, so the vehicle is driveable.