Engine and Transmission Noise

Occasionally noise that appears to be from the differential is actually caused by the engine or transmission. To identify the true source of the noise, note the approximate vehicle speed and/or RPM when the noise is most noticeable. Stop the vehicle next to a flat brick or cement wall (this will help reflect the sound). Place the transmission in NEUTRAL. Then vary the engine RPM slowly up and down through the engine speed that corresponds to the RPM noted. If a similar noise is produced using this method, the noise is being caused by the engine or transmission, not the differential assembly.