My boyfriend just replaced his front hub bearing 4 weeks ago and it is already completely out again. What could be causing this he has a dodge ram 1500 4x4

 

Few things to check for - defective replacement hub bearing, incorrect torque applied to retaining nut, U-joint behind the hub bearing bad and binding up.

 

What kind of tires and wheels are you running ? are the ball joints and tie-rod ends good? Have you had a wheel alignment lately? Did you torque the axle nut properly . Did you make sure that the bearing was seated completely flush? all these things can and will lead to premature bearing where in the hub.