Park the car at the side of the road and put the parking brakes into action. Find the jack inside your car tool box and put it at the front end of the car; tie it with a safety stand so that it doesn’t do any damage to the exterior your car that will result in extra investment.
Look up for each axle and the differential for any faults or irregularities. Browse the boots and see if you can find any sort of grease of tears that might have stopped the whole system to work.
Move the wheels from one side to another and inspect every part of the axle for any signs of hidden rips or wear and tears. Don’t leave anything and give a benefit of doubt to any portion of the axle that you can’t access. Don’t be lazy because it can cost you a lot.
See if the movement of the boots is restricted by something while you turn the wheels. If there is some problem, it means that the grease has jumbled up across some are of the axle that is stopping the free movement. There should be no noises during the wheels rotation otherwise something is wrong.
List down any irregularities you find and repair it instantly or call some expert to do it for you but don’t move the car without rectifying the problem.
Get rid of the safety stands and jack down the car to its usual height.