1997 z71 4wd

I have a 1997 z71 with push putton 4wd. A few days ago when going down a bumpy road in 4wd the switch on the dash began to flicker and I heard what I thought was a relay type noise (relay on/off) and then the 4wd no longer worked. I went ahead and replaced the actuator in the front differential because these seem to be problematic but that did not solve the problem. I also replaced the dash switch that switches 2-4wd and that did not solve the problem. I don't believe the problem is mechanical but rather electronics. Where's the best place to continue my search for the problem??