Q: How do you detect the grinding noise in the rear diferential, rear wheel drive?

Hi there. Raise up the vehicle off the ground and put it on jack stands where all the wheels are off the ground. Check the rear differential fluid in the rear axle on the car. See if there is fluid in the differential. If there is no fluid, then fill up the differential with the gear oil that the vehicle came with from factory and recheck for any noise. If the fluid is full, start up the vehicle and step on the service brakes to the floor. Put the transmission in low and let off the brake. If the differential was damaged it will make a noise like grinding or a banging noise. If there is no noise, then shut off the engine and put the transmission in park when the wheels stop turning. Lower the vehicle and take the vehicle for a test drive. With all of the windows down, if there is a grinding noise, then the differential or transmission may be damaged to where only a load will cause the sound. This would be a bearing in the differential or transmission failing. If you need further assistance locating the grinding noise under your vehicle, then seek out a professional, such as one from Your Mechanic, to help you.