Mud pumps work hard in dirty, demanding conditions,dealing with high loads, high temperatures,contamination and vibration.  Order Mud Pump Sets with bearings for all four bearing locations in most mud pumps.
The largest load bearing area of the pump is the crosshead pin and bushing area. Wear can be detected by locking the intermittent or piston rod with a pipe wrench and rotating the crank shaft slightly. If one can feel any slack it can only be coming from the pin and bushing or the connecting rod bearing. It then becomes necessary to remove the connecting rod assembly consisting of the connecting rod and cross head. If slack is determined in the pin bushing, it will be necessary to press out the pin and inspect the bushing and the crosshead pin in the eye of the connecting rod. Some manufacturers ship bushings that are designed to fit. Others ship them and they have to be reamed to fit the pin after the bushing is installed.