I have a 1975 Ford F-150 4x4 that I am working on restoring and modifying. I am currently going through the Dana 44 front axle, and I was curious how you can tell if a wheel bearing is spinning on the spindle. It appears that is exactly what is happening in my case. The bearings and spindle look fairly new.
Based on your photos we agree that the inner bearing has been spinning on the spindle, and that’s not good. If left unattended, the bearing will eventually friction-weld itself to the spindle, which is both costly and difficult to repair. It looks like you caught yours in the nick of time, as it has clearly gotten hot at some point. The grooves visible on both the spindle and the inside of the bearing are the telltale signs, and the discoloration indicates heat. Run your fingernail along the grooved area of the spindle; if you can feel those grooves but they don’t seem very deep, you might be able to clean up the spindle with emery cloth. If not, you should replace the spindle. We would replace the bearing regardless.
Wheel bearings can spin for many reasons, among them lack of lubrication, improper setup, contamination, or just age. Here is the basic procedure that we follow. First, periodically check the wheel bearings for play by jacking up the axle on one side, grabbing the top and bottom of the tire, and attempting to rock the tire back and forth. If you feel any play, the bearings are loose. Next, with the tire still off the ground, rotate it. It should spin freely, with just a very small amount of drag. Remove the locking hub and have a look inside. If there are any signs of water or contaminated grease, it’s time to service the bearings. There should also be lots of grease visible. If the bearings don’t look nasty, there isn’t enough grease on them. Pull the tire and wheel hub and have a look at the inner bearing and seal. If all checks out, reinstall the hub. Run the first spindle nut down firmly to seat the bearings, then back it off. Tighten it again to just past where you start to feel resistance. Install the locking retainer, followed by the second nut. Tighten the second one firmly, then rotate the hub. It should spin but have just a little drag on it. If it doesn’t or there is play, back the nuts off and start over. Once satisfied, secure the locking retainer if applicable.
One last thing to check specific to your Ford since you said the components look fairly new. Ford used a couple of different spindle, bearing, and wheel hub combinations right around your truck’s vintage, so you might want to make sure that all of the components match. That will be difficult to do if you don’t have the original parts, but you should be able to track down all the pertinent information if you can find the axle BOM number. It will be on the differential tag if the tag is still present, and it is usually stamped somewhere on the long side axletube.