Have turned switch to 4W Drive High & turned hubs to lock position but 4W drive will not engage.

Sounds like a transfer case related problem. First, check all under hood and under dash fuses with a test light or multimeter. Second, check for codes. Third, check the transfer case itself. Fluid should be changed every 100,000 miles--I use 2 quarts of Mobil 1 Synthetic ATF.

Will try this tomorrow. You can hear it try to switch & we hear a rachet sound when we try to engage.