Signs and sounds of transmission problems. In the automotive world you have two types of transmissions. You have manual transmissions which require the driver to shift gears manually. And you have automatic transmissions where the transmission itself determines what gear is appropriate for the given speed and load. Transmissions like any other mechanical device wear out over time and can fail. And some signs of a transmission that is pending failure: noise of any sort that is out of the ordinary, whether it's grinding gears or whining sounds, anything that does not sound appropriate usually is not. A manual transmission generally is simpler and therefore has fewer parts to fail than an automatic transmission, but there are still components that can cause problems. If the transmission is not lubricated properly, the gears can wear out and get improperly fitting, which will cause gear noise. The syncromesh which smooths the gear shift transition can wear and cause gear shifting issues, and the bearings themselves can wear and either seize or make noises. On an automatic transmission, the bands in the transmission which are responsible for selecting the various gear ratios can begin to slip. They can wear out due to abuse or neglect. The valve body itself which is responsible for sending fluid to various components in the transmission can become plugged or can get debris in it that can cause shifting problems. And the best solution against that is proper fluid and filter changes at the manufacturer's recommended interval. The other potential issue with automatic transmissions is overheating due to insufficient fluid in the transmission or insufficient cooling in general.