4x4 not working

ok i had the shop check my 2001 4x4 because the lights
on switch blinking and they said encoder motor bad 600$
to fix so i found one and fixed myself and rest comp..
and lights work - encoder motor works - vac. lines work -
every thing seems to work but front wheels are not pulling. i lifted front up and turned wheels by hand
to see if in 4wh and they turned front axle,moved out of
4wh and wheels moved free. so if 4wh engages but doesnt
work what is it, i called shop they said maybe front
axle clutch sleeve . help please

2001 blazer