When you're not familiar with the inner structure, the function of your car's transmission can be mystifying. Unfortunately, it can also leave you stranded if you're not able to recognize early signs of trouble. When it comes to automatic transmissions, one of the most commonly overlooked signs of trouble is hard shift response. If your car's transmission isn't shifting smoothly anymore, it may be a sign of a problem. Here are a few things you should check out when your transmission starts shifting too hard.

Examine the Fluid Condition

The transmission relies on sufficient clean fluid to keep everything moving properly. Check the condition of the transmission fluid using the dipstick that's under the hood. The fluid should be clear and free of any discoloration, cloudiness or debris. Clean transmission fluid is usually fairly translucent and red when it's fresh. Anything other than that indicates wear or possible damage to the transmission. The darker the fluid is, the worse it's condition. The fluid level should also be within the "full" range on the dipstick. If it's low, top it off. Check the level periodically, and talk with a transmission mechanic if you're regularly losing transmission fluid.

Test the Computer Codes

One of the great things about the computerized nature of new car engines is the storage of trouble codes on the engine computer. If there's a sensor failing or a problem with the control module in the transmission, it will send a trouble code signal to the car's computer. Any mechanic or auto shop can plug a scanner into your car's computer port to read the trouble codes stored in the system. Sometimes, this will make it easy to identify the source of the problem.

For example, if the speed sensor is failing, it's known to cause hard shifting. This happens because it relays inaccurate information about the car's actual speed of travel, which can cause the transmission to shift either too early or too late. This may cause a hard shift. If the speed sensor is faulty, a quick scan for trouble codes will reveal that fact.

Assess the Integrity of the Vacuum Lines  

If you've eliminated the easier troubleshooting tasks without discovering the source of your shifting trouble, you'll need to test the vacuum lines in the transmission. Sometimes, these lines can come loose, bend or clog up with debris. This can lead to shifting problems, because it disrupts the vacuum balance required for the gears to shift smoothly. You'll need a transmission technician like Northgate Transmission LLC to check and clean these properly.