switched on 4wd but front wheels did not spin?

got stuck in mud. switched on 4wd but front wheels didn't spin. i remember traction control doing that on an Impala but i see no button for it. Suburban in that situation switched on right away, but not the Tahoe. lights lit telling me 4wd was on. Neither high nor low would spin the front tires. Is there traction control on the truck? some forums say 4wd will not engage after you're stuck is this true? or is it broken? it clunks when you turn it on as though it is engaged.