From Timken bearings site:
* Orange area indicates the recommendation for the correct amount of grease to be packed into the bearings prior to installation on grease-lubricated wheel ends.
* Work grease into the bearing underneath the cage towards the large rib.
For best results, ample space is essential in the housing to allow room for excess grease to be thrown from the bearing and for heat dissipation. It is equally important to retain the grease around the bearing. Normally, the housing should be 1/3 to no more than 1/2 full of grease during bearing assembly. Too much grease in the housing may cause excess churning of the grease and high temperatures.
Statistics show that nearly 50 percent of all bearing damage can be attributed to inadequate lubrication. Although a very broad term, inadequate lubrication can be classified into eight basic categories: 1) overfilling, 2) underfilling, 3) incorrect grease, 4) mixing greases, 5) incorrect lubrication systems and intervals, 6) worn-out grease, 7) water contamination, and 8) debris contamination.
Overfilling a bearing with too much grease can cause excess churning of the grease during operation and high temperatures, resulting in overheating and excess grease purging* (leaking). Overheating occurs because the heat generated cannot dissipate correctly, continually building until damage occurs. As the operating temperature of the bearing rises, the oxidation (breakdown) rate of the grease sharply increases doubling every 18ｺ F.
Underfilling a bearing with grease can also have adverse consequences. As in overfilling, heat can be generated but for different reasons. When the grease amount is low, a grease starvation condition may be created, causing heat generation or excessive metal wear during operation. If a bearing suddenly becomes noisy and/or the temperature increases, excessive wear may be taking place.
Bearing end play should be in the .001"-.005" range for non-drive front axles, drive axles and trailer axles.
