For 1990-2009 cars

Cause | Correction
--- | ---
Inspect for the proper gear oil levels prior to performing system diagnosis. Refer to Axle Lubricant Change .
Incorrect type fluid Installation of the incorrect type gear oil may create a "moan" type noise within 7 770-25 900 km (3-10,000 miles). Fluid that is "black" in color is to be considered normal and is darkened by the carbon material in the clutch plates. | Replace the rear differential assembly as required. Fluid replacement will not correct a "moan" condition caused by the use of incorrect oil. Refer to Differential Replacement .
Water or contamination within the transmission oil Water or contamination within the transmission fluid, causing excessive torque converter clutch slip rate, may create a "grind, growl, or moan" in the rear differential or torque tube under light or steady load conditions. | Replace the transmission fluid and flush the transfer case of the contaminated fluid.
Loose propeller shaft mounting bolts | Tighten the bolts as required. Refer to Propeller Shaft Replacement.
Worn propeller shaft constant velocity joints | Replace propeller shaft assembly. Refer to Propeller Shaft Replacement.
Worn axle shaft constant velocity joints | Replace the constant velocity joints as required.
Worn, loose, or missing differential mounts | Repair or replace the differential mounts as required.
Loose torque tube bracket or a worn bracket bushing | Tighten the bracket bolts or replace the bracket as required.
Worn bearing in the torque tube assembly | Replace the torque tube assembly
Torque tube dampner loose or missing A "moan" or "exhaust leak" type noise at higher engine speeds, approximately 2,000-2,500 RPM, may indicate a loose or missing dampner. | Tighten the dampner retaining bolt or replace the torque tube assembly as required.
Bearing noise within the differential assembly A "grinding" or "roar" type noise will increase or decrease relative to the vehicle speed. |

1. Check for the proper fluid level. Fill as required.
2. If the noise continues, replace unit as required.

Gear set "whine" noise within the differential assembly A "whine" type noise will increase or decrease relative to the vehicle speed approximately 80-97 km/h (50-60 mph). |

1. Check for the proper fluid level. Fill as required.
2. Replace unit as required.