2002 Chevy S-10 4x4 not working. Low gear will engage, but

I was wondering if there was a quick way to determine if my 4x4 actuator is shot on my s10. When I press my 4x4 button on the dash, the light goes on, I can hear typical noises, but the 4x4 does not work. i was lucky enough to find this out while offroading. seems as if it has taken longer to engage recently, now not at all. any ideas? Thanks!
John