Noise in a spiral bevel gear set is usually a sign that something is off in assembly, alignment, or lubrication. The most common cause is incorrect mounting distance — if the pinion is not positioned exactly where it should be relative to the gear, the tooth contact pattern shifts to the toe or heel, creating noise. Another frequent issue is improper backlash, either too tight or too loose. Insufficient lubrication or using the wrong oil grade can also cause rough operation. Housing deflection under load may disturb gear alignment. Less common but possible causes include manufacturing errors such as runout, tooth spacing deviation, or poor surface finish. Belon supports our customers to analysis the possible reason and offer technical support all the way if any quality discrepancy happened.