Gear Noise

There are two basic types of gear noise. The first type is produced by broker), bent or forcibly damaged gear teeth and is usually quite Audible over the entire speed range and presents no particular problem in diagnosis. For example, hypoid-gear tooth scoring generally results from the following: insufficient or improper lubricant, improper break-in, insufficient gear backlash, improper ring and pinion Gear alignment, or loss of drive pinion nut torque. The scoring will progressively lead to complete erosion of the gear tooth or gear tooth pitting and then eventual fracture if the initial scoring condition is not corrected.

Another cause of hypoid tooth fracture is extended overloading of the gear set. This will produce fatigue fracture or shock loading, which will result in sudden malfunction. Differential Pinion and side gears rarely give trouble. Common causes of differential malfunction are shock loading, extended overloading and seizure of the differential pinions to the cross shaft resulting from excessive wheel spin and consequent lubrication breakdown.











The second type of gear noise pertains to the mesh pattern of the gear teeth. This form of abnormal gear Poise can be recognized because it produces a cycling pitch (whine) and will be very pronounced in a particular speed range. The gear noise can occur in either "Drive," "Float" or "Coast" conditions. "Drive" is acceleration or heavy pull. "Coast" is when no acceleration takes place and the vehicle is in gear. "Float" happens when just enough acceleration occurs to keep the vehicle from driving the engine; the vehicle slows down gradually but the engine still pulls slightly. Gear noise tends to peak in a narrow speed range or ranges, and will tend to remain constant in pitch. Bearing noise will vary in pitch with vehicle speeds.