Iford1995

Hi, I have a 1995 Ford F150 Pickup 4x4 automatic transmission with Manual Lock-Out Hubs. When I lock in the hubs all is fine if I am going forward. If I back up The front wheels will not spin. If I step on the gas and spin the rear tires (on Ice) the front hubs make a "low" grinding noise llike they are not quite engaged. I hear this on BOTH sides. Going forward all seems to be fine. Going forward The front wheels pull fine and seem to remain engaged. I have driven throw the snow with no problem as long as I dont try to back. The truck will back up but if I spin on the ice i am stuck because of the hub problem. Last summer I had a mechanic replace the front ball joints. Could he have caused this problem? I never had this issue last year. If anyone has any ideas please let me know??

Thanks