An automatic transmission is designed to make driving easier, as you need only put the shifter into drive to move forward. Manual transmission vehicles require the driver to shift between gears as the car moves faster, which does offer more control, but the automatic system does all of the in-between work for drivers these days. The inner workings of an automatic transmission can be rather complicated, and anything beyond minor problems will typically result in the system needing to be rebuilt or replaced. The earlier you catch a problem, the better your chances are of avoiding extensive work to get things up and running.
If your transmission is acting up, whether the gears are sticking or slipping, there could be a number of factors affecting the system's performance. The first and easiest aspect to check is the transmission fluid. Low fluid levels, whether or not they are caused by leakage, can cause a slew of problems.
When the transmission system does not have enough fluid to lubricate its parts, it can easily overheat or make shifting difficult. If you detect low levels, you should add more liquid. This should fix whatever problem you are experiencing - including whining sounds, overheating, gear slippage or internal fluid leakage.
In all likelihood, low fluid levels are indicative of a leak. You should address this issue as soon as possible. Otherwise, you will continue to encounter the same issues and eventually cause extensive damage to the transmission. Check the hoses and seals of the transmission system for signs of leakage, and keep an eye on the ground below your car when you park it overnight. Drops of reddish liquid on the ground can help you locate the area where the leak may be.
If the fluid level is fine, but you are still experiencing issues, check the quality of the liquid. It should be changed relatively frequently, as the constant exposure to high temperatures will degrade it quickly over time. A good rule of thumb to follow is to have the fluid checked twice a year, but every vehicle is different. Consult your owner's manual for more exact scheduling advice.
Another aspect of the transmission system that could cause problems if ignored is a clogged filter. This easy-to-fix issue is something few drivers consider, but it is a good idea to replace the filter every 30,000 miles or so. Every vehicle differs, so be sure to consult your owner's manual or a model-specific repair guide if you opt to replace the filter yourself.
Another issue that could result in a full-scale transmission rebuild or replacement is faulty transmission shift solenoids. These electro-hydraulic valves are designed to open and close to control the flow of fluids throughout the system. If they get stuck, the control will be lost and the transmission will likely begin to act up. The torque converter is another part of the system that could cause trouble if it breaks. This part is responsible for connecting the engine to the transmission, and plays the same role as the clutch in a vehicle with manual transmission. If the converter gets jammed, it can result in a loss of power at high speeds or overheating when cruising. A faulty torque converter can also result in debris making its way into the transmission fluid and a loss of fuel economy.
Regardless of what the problem is, it is important to address transmission issues as soon as possible. Otherwise you will inevitably need to rebuild your transmission, which is typically a costly venture.