I have a 1998 2500 5.9. 24valve 4x4.
I was driving the other day an my front end (axle) started grinding so i pulled off an put it park .i checked the front end an nothing lookd messed up ot outa the ordinary so i gp to leavw an put it in drive an it started grinding like it was tryng to lock in 4wd .i shut it off put it 4by an she drove fine home . i replaced the vaccum actuator an checked the vaccum lines an went to try it out an made it a block down the road an the front end started to grind . i put it in 4by again an it made it home fine any ideas onto what the problem is?

 

Did you check the nylon pads on a shift fork when you changed the actuator? If they are worn, locling collar might get in contact with intermediate shaft (which is turning opposite direction to the outer shaft in 2wd).

 

It came with a new set to swap out