There are few things quite as terrifying as a transmission problem. A failing transmission can often be the most expensive item to repair on any vehicle outside of internal engine damage. Because the potential costs can be so high, it can be especially troubling when you get into your car and discover that it won't shift into drive.

Fortunately, you may not need to panic if you can't get your car's transmission out of park. As it turns out, one of two relatively simple problems may be to blame.

Stuck In Park? It May Be Your Shift Interlock

What's the first thing you do when you get into the car? You might think the answer is "turn the key," but it's more likely that you push your foot down on the brake pedal. This action comes so naturally to most drivers that you may not even consciously realize that you're doing it. The reason is simple: you can't put an automatic car into drive if your foot isn't on the brakes.

The component that prevents your car from shifting into park is called the shift interlock solenoid. This simple part acts as a safety to keep your vehicle from unexpectedly moving forwards or backward. Since automatic cars will begin to move as soon as you release your brake, this safety feature is crucial in preventing accidents in parking lots and driveways.

Since the shift interlock is as much about safety as it is about the operation of your transmission, a failed interlock will usually prevent you from moving out of park at all. Although the price and replacement difficulty vary between models, replacing this component is typically cheap and straightforward.

Car Won't Move? Check Your Fluid Levels

What happens if you can physically move the shifter into drive, but the car won't engage any gears? Unfortunately, this might be a sign of a more severe problem. Before panicking, however, check your transmission fluid levels. Your transmission relies on proper fluid levels to provide pressure to shift gears, so you may not be able to get into gear at all if the level is too low.

Keep in mind that your transmission is a closed system, and you should never lose transmission fluid. Losing enough transmission fluid to prevent your vehicle from getting into gear is a sure sign of trouble. Try topping off the fluid, but avoid driving your car as much as possible. Since low fluid can result in more severe damage to the transmission, you should immediately schedule a service appointment.