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DRIVELINE TIPS IV
FAILURE ANALYSIS
1. Shock Load is failure where engineered values are exceeded and sudden sharp spike in load value will
shear related parts. Clean break in appearance.
2. Brinneling is where the needle bearings will embed themselves into the trunnion surface, due to lack
of movement (rotation) and lube. Appearance will be multiple ridges around the trunnion surface.
3. Galling is the condition where due to lack of lube and the presence of heat, two metal
surfaces will weld, fusing together. The bearing cap will become permanently attached to
end of trunnion.
4. Spalling is where due to foreign presence of material (moisture) lube will be diluted and
no longer protect against heat resulting in eventual failure.
5. Fatigue is where due to time, heat, stress loads and various chemical exposures to
materials, the surface will began to deteriorate and break down. A surface pitting or
flaking will occur resulting in structural weakening and eventual failure.
6. Beach Marks are visual markings on failed surface related to shock load. You can see cracks, fissure
marks on surface that increased over time prior to ultimate failure.
7. Critical Speed/Tube Failure is where tubing collapsed, crimped, separated due to shock
load / critical speed.
8. Imbalance issue is when weights are missing or placed too close to tube weld seam.
Can cause static vibrations as a jump rope, resulting in ultimate failure.
9. Lube recommended is NLGI EP 2. Lack of proper lubrication will result in premature
failure.
10. Driveline slope should have a minimum of 1/2° to spread lube in the U-joint bearing caps, and avoid
failure due to lack of lube.