4WD Class 101

[3quartertime]

Got a problem. Either I don't know how to engage the 4WD in my truck or it doesn't work. Truck is a 71 K20 with spicer lock-outs. Don't know the type transfer case or front end.

I spin the lock-out hubs to lock and with the truck in neutral I try to engage 4-lo. Only back tires spin. Tried 4-hi same thing. Can't turn front drive shaft with hand in either. But in 2-hi it turns by hand. So I'm thinking the tranfer case is working, thou I haven't actually seen the driveshaft spin while the truck is moving.

Sooo,,, either I don't know how to engage 4WD in the truck ( Which I would be grateful if someone could school me!!!) or my lock-outs aren't working. Or a little of both!!!

If it's the lock-outs what is the most likely problem?

Thanks for any help...