The drive shaft of your car, used mostly in rear wheel drive vehicles, sits between the transmission and rear differential, which in turn is mounted on the rear axle, making use of various CV joints and universal joints in an intricate system. Although this sturdy piece of mechanics generally has a long life, hardly needing to be changed as often as something like the brake discs or brake pads, the drive shaft will, from time to time, require maintenance.
Common sign of a part that is worn and requiring maintenance is the development of unexpected vibrations. These can be felt in the floorboards of the vehicle when stationary or in steady motion, and will gradually increase over time as the problem worsens. Take note of such symptoms and be sure to act in a timely fashion as the greater the problem becomes, the more damage can be done to other parts of the system, greatly increasing costs. Also remember to test your glow plugs, to ensure your car starts and performs smoothly.
When a problem is suspected, it may be possible that a joint has worn, and not the shaft itself. In this case, a savvy car owner may be able to replace the joint DIY, saving money and avoiding expensive trips to the mechanic. It is possible to buy a simple kit containing a joint, which may be fitted with a little elbow grease. Take note that free, detailed instructions for such jobs can be easily found online.