How can you tell if a rear end is out?

To determine if a rear end is out, listen for unusual noises such as grinding or whining while driving, especially when accelerating or turning. Check for fluid leaks under the vehicle, as low or contaminated differential fluid can indicate issues. Additionally, inspect for play in the wheels by shaking them; excessive movement could signal worn bearings or a failing differential. If you experience vibrations or handling issues, it's also a sign that the rear end may need attention.