Ans: You can tell that your differential needs oil by several signs: *Whining or Howling Noise: If you hear a whining or howling noise coming from your vehicle, especially during acceleration or cruising, it could be due to insufficient lubrication in the differential. *Leaking Fluid: Visual inspection may reveal leaks or seepage around the differential housing, indicating a loss of oil. *Erratic Handling: A poorly lubricated differential can affect your vehicle's handling and stability, leading to erratic behavior, especially during turns. *Regular Maintenance Schedule: Lastly, it's essential to follow your vehicle's recommended maintenance schedule, which often includes regular differential fluid changes. If you're unsure when the last change was performed, it's a good idea to have it checked to ensure proper lubrication.