whining sound coming from sounds like transfer caseany ideas
 

i took my 01 blazer ls 4x4 to a shop for new intake gasket also told them to check 4x4 because front wasent locking they said no problem with the 4x4 but still dosent work since they worked on it i hear a whining sound coming from somewhere around the transfer case does anyone have any idea what i need to check first?