With a worn balance shaft bearing on the front of your engine, the level of vibration emanating from it will constantly be increasing the longer this component is kept on the vehicle. The way the balance shaft bearing can become worn is from dirty motor oil circulating in the engine. What most owners are not aware of is when the oil filter becomes clogged, it activates a bypass valve and the oil just continues to circulate without any filtering element cleaning the oil. This is when small pieces of dirt can enter the bearing causing it to become scorned which increases the level of resistance it has when it is rotating.
The balance shaft bearing is a ball bearing that has multiple balls which circulate between an outer and inner race. This is encased in a steel housing so the minimal amount of exposure to any contamination is made. The material the casing, ball bearing and races are made from is a hardened steel alloy. The location of the balance shaft bearing is on the front lower section of the engine block. It is next to the crankshaft under the timing belt or chain cover. It is just like the crankshaft bearing, but is just a little bit smaller in diameter.
To replace the balance shaft bearing requires that the timing chain or belt cover be removed and more than likely the balance shaft removed from the engine. This requires all of the components on the front of the engine to be removed like the alternator and water pump. For more clearance, the radiator might also want to be pulled so access to the front of the engine and the balance shaft bearing is possible.