WTB small 4x4 farm use truck, any advice?

[BLINGMW]

Any easy way to test that the 4wd works today? Am I understanding correctly that the front hubs need to be locked as well as engaging 4hi or lo to get it to be in 4wd? Or should the hubs only be locked when on loose surfaces? All I know so far is the dash light works, and I could feel the gear ratio change in 4lo.