The images below are provided to help you make an accurate Differential Failure Analysis. A visual inspection of the failed or damaged ring and pinion gears and/or bearings will usually indicate the cause of most failures.
Normal Ring and Pinion Wear:
The tooth surface on the ring and pinion gears is only moderately shiny. The machining striations on the drive surface of the ring gear teeth are still visible (on the actual gear set, if not in the attached picture). The face or edge of the pinion gear teeth is still squared off. This ring and pinion set shows normal wear. Click Here for a larger image
Burned Ring and Pinion:
This ring and pinion set has been burned so that the tooth surface is very shiny. The machining striations are no longer visible and there is a hard edge at the root of the ring gear teeth showing how much the surface has been burned off. The face or edge of the pinion gear teeth is worn to the point of being sharp. Burning like this is caused by lubrication failure. There was not enough oil in the differential, or the differential was not properly set up, became too hot, and the oil broke down. Click Here for a larger image
Very Burned Ring and Pinion:
This ring and pinion set shows excessive heat failure. Much more of the gear tooth surface has burned off than in the example above. The pinion gear teeth have worn down to a very sharp edge. Again, the cause is lubrication failure. Click Here for a larger image
Broken Ring and Pinion:
The teeth have been sheared off this ring and pinion set. This is evident in the dull grey areas. The shiny areas have been hammered by the broken gear pieces. This does not indicate that the ring and pinion gear set was defective, but rather that too much power was applied with too much resistance in the tires. This can be caused by too much power combined with oversized tires or tires that are stuck on an off road obstacle. Spinning tires that suddenly catch either off road or on the track can break differential parts as well. Click Here for a larger image
Pitted Bearing and Race:
This degree of pitting can be normal for bearings with over 100,000 miles. This bearing and race would be very noisy. See Diagnosing Differential Problems. Pitting can also be caused by excessive preload and by limited lubrication failure. Extensive lubrication failure will often cause the roller cage to melt, which has not happened in this case. Click Here for a larger image
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