Pinion bearing failure

[Eric Worpe]

Are we maligning the pinion bearing unfairly ? It seems to have to withstand a stressful life, not just due to the axial loading of the pinion as it tries to climb out of mesh with the crown wheel but also vibrations due to "cogging"; a result of the universal joints on the prop. shaft not being in the same plane because as Neil Nelson pointed out, the brackets on the back axle mounting have broken Even if the brackets are sound, the prop. shaft might be out of balance, putting a harsh radial load on the pinion bearing. All of these stresses could combine at speeds up to 5000 RPM within a suspect lubrication environment, one only has to look at a modern back- axle with substantial oil galleries to the pinion bearing cast into the diff's nose piece to realise that the Tabc pinion bearing was lubricated more by luck than design. Could it get any worse ? Well Mark Jablonski puts a good case for stress corrosion in the cage and then Joe Curtoe delivers the coupe de grace by revealing that the bearing was overrated even at the drawing board stage. It's a wonder it lasted so well. Bob Grunan and Roger Furneaux both suggest fitting taper rollers, well I wouldn't argue, they are even cheaper. Regards, Eric.