Diagnosing a problem in your car can sometimes be the most problematic part of the process. For instance, if there's something wrong with your driveshaft or drivetrain, then you're going to hear strange noises and feel unusual movements. However, if you're not sure what you're looking for, diagnosis can be almost impossible.
One of the easiest symptoms of a driveshaft problem to diagnose is the vibrations that occur. If you have a driveshaft issue, the floor of the vehicle is going to vibrate. This will be noticeable at almost any speed, but it's even more noticeable if you're driving at a faster speed (50 miles per hour and up). The vibration is noticeable through all parts of the vehicle, though it's strongest at the floor and weakest toward the higher parts of the car.
Another symptom of a driveshaft problem could be difficulty in turning. If you're trying to turn your wheels and they're resisting, the problem could be in your driveshaft. However, the problem could also be in your universal joints, which are connected to the driveshaft. The only way to be sure is to raise the car up and look. You could also remove the driveshaft and try to turn the universal joints. If they turn freely, chances are that the problem might be in your driveshaft.
While vibration is more common as a symptom, there might be unusual sounds coming from beneath your car. Knocking sounds, metallic grinding or even squealing could all be symptoms of a driveshaft or a drivetrain problem. The sounds come from the central area of your car and are in the floorboards. If the bearings are at fault, then the noises come from closer to the wheels than from the centre line of the vehicle.