Because the 1979 Corvette uses the two rear tires to propel the car, it was equipped with a differential. Within the differential are two gears and a number of bearings. When noise emanates from the back of the car, the noise is usually attributed to the differential. However, rear end noise can also be caused by improper tire pressure, improper tires or by a damaged wheel bearing or loose exhaust system. Because the differential’s two gears mesh, some noise is normal. Fortunately, determining the cause of excessive rear end noise is fairly simple.
Stop the car and place the transmission in neutral.
Apply the parking brake and depress the brake pedal, then raise the speed of the engine with the accelerator pedal. If the noise is still present during this test, the problem is likely with the engine or the exhaust system, not the rear end.
Drive the Corvette for approximately 10 to 15 minutes to warm the differential fluid.
Make sure that the tire pressures and the differential fluid level are normal. Inspect the tire’s sidewall for the proper pressure, as the pressure level varies depending on the type of tire. Remove the drain plug from the center of the differential with a wrench to check the rear end fluid. The fluid level should be just below the bottom of the drain plug’s opening.
Drive the Corvette over several different types of road surfaces to determine if the noise is being caused by the rear end or by the tires. If the noise is produced only when the car is driven over a rough surface, the noise is most likely caused by the tires.
Drive the Corvette on a smooth surface until the noise is produced. Lightly depress the brake pedal. If the noise disappears, the problem is likely a damaged wheel bearing. If the noise does not disappear, the differential’s pinion gear is probably damaged.
Turn the car sharply and listen for the noise. If the noise is present, the problem is likely improperly adjusted ring and pinion differential gears or damaged pinion shaft bearings.
