Transmission problems are one of the most serious and expensive vehicle issues to repair. Transmissions typically cost upwards of a thousand dollars to fix and, if not functioning properly, can render a vehicle completely immobile and unusable. When a transmission begins exhibiting signs of problems, it should be taken to a transmission expert and serviced as soon as possible to avoid incurring serious damage. In some cases, catching a transmission problem early can prevent transmission failure.
Check your transmission fluid. If your transmission is low on fluid, or if the fluid is old and discoloured, it could be to blame for the hard shifting. Hard shifting can occur due to a lack of lubrication in the transmission. Transmission fluid should be reddish in colour and largely transparent.
Most modern vehicles are equipped with a wide assortment of sensors, including those that control how and when your car's transmission shifts. If the sensors are not receiving the correct signals and readings, it can lead to shifting problems. Hard shifting may be caused by a slow sensor or one that is transmitting the wrong signals from the engine. A faulty speed sensor may be to blame for reporting that vehicle is running more slowly or more quickly than it actually is.
Problems with the vacuum lines on a transmission have been known to cause hard shifting. Clogged, bent or disconnected vacuum lines affect the pressure in the transmission and can cause rough shifting to occur.
The transmission control module on your car stores transmission error codes. If you are having a difficult time diagnosing why your transmission is shifting hard, you can take your vehicle to a transmission service mechanic and have these error codes read. These codes should give you a good idea as to why your transmission is shifting hard and how it can be repaired.