So I had this guy send in the following U-joint today and I pulled it open. Simple diagnostic. I wrote up the report and sent it to him. He calls me and tells me this is the best thing he has ever recieved from a supplier and that we had is biz for ever and ever. No big deal to me...
Conclusion
The failure was likely generated by metal-to-metal contact due to
lubrication boundary starvation. The resulting particles that were generated persisted in creating more wear. Starvation may have occurred due to a blocked grease channel or infrequent greasing. It is difficult to determine the exact cause of the starvation.
Recommendations for Greasing U-Joints
Apply grease until new grease purges from all journal cross bearing seals. Make sure the new grease is flowing from all four seals or loosen bearing cap bolts until it does (if it doesn’t purge from all four caps, replace U-Joint.
Additional General Recommendations
New Bearings
Always store new bearings in their original wrappings away from
contaminants such as dust, dirt and moisture. Never heat
bearings. Heating bearings may change the temper of the metal.
Maintain A Clean System
Always clean grease fittings and grease gun before and after each
application. Never allow the grease pump to touch the ground or any
other source of contamination.
Packing Bearings
An easy rule of thumb when packing bearings is to fill to 50%
capacity of the bearing. The following equation can also be used:
Grease Amount (grams) = 0.005 x Bearing Width (mm) x Bearing
Outer Diameter (mm). Always consult the manufacturers
recommendations.
Greasing Plain Bearings
Initial charge should be at an angle between 90° and 180° from
the grease fitting or grease entry side.
Greasing Vented Housing Bearings
Remove the vent of the bearing once it is stopped. Apply grease
until it flows from the vent opening. With the vent still removed,
slowly rotate bearing so excess grease can escape. Replace
vent and clean housing.