4x4 activation problems

i have a 2004 silverado and i cant get the front hubs to lock.It has the 4x4 shifter on the floor it can shift from 4h to 4l and it will go into gear,but it just wont lock.....please help

Is the 4x4 light coming on in the dash?

Ya, we need more info. What do you mean by lock and what is it your expecting to happen when you shift that that thang. People have different interpretations of what locked means.....jj

all the 4x4 trucks from 90 on all have automatic locking hubs. so it is either going into 4wheel drive or not. when you shift it into 4L the xfer case may ingage the transmission but may not be engaging the front drive shaft.. if that is the case there will be an issue with the xfer case. $$$

There hasn't been a locking hub on a 1500 series since 1987. These use a central axle disconnect.