Why is My Transmission Shifting Hard?

When your vehicle has transmission issues, it can be pretty apparent. Second to the engine, the transmission is one of the components that makes a car move. Every time you pull out of the driveway, accelerate onto the highway, or slow down for a red light, the gearbox is working to keep your car in the optimal gear. With so many gear changes happening every time you drive, if something isn’t right, you’ll notice it quickly. 

A common transmission complaint is hard shifting. If you are used to smooth, nearly imperceptible gear changes as you drive, a sudden switch to harsh, clunky shifts is concerning and can be indicative of transmission problems. In this article, we are going to go over some of the most common causes of a hard shifting transmission. 

What Is Considered Hard Shifting?

A hard shift can present in a few different ways. You may notice a delay when you expect a gear change to happen, followed by a hard, even audible clunk as the next gear is found. Rough shifting can impact how your vehicle accelerates and the overall comfort and driveability of your car.

What Causes a Hard Shifting Transmission?

There are a few things that can cause changes in how your gearbox is shifting. Some causes are related to lack of maintenance, while others may be caused by mechanical issues in the transmission.

Low Transmission Fluid

Conventional automatic transmissions use a specialized hydraulic fluid to initiate gear changes, lubricate internal parts, and keep things at a safe operating temperature. If your transmission has low fluid, it can have a direct and immediate impact on how it shifts. If it’s determined the fluid is low, topping it off will sometimes solve the problem. However, finding the root cause of the low fluid is essential to prevent further shifting issues and damage to the transmission. 

Causes of Low Transmission Fluid

Most of the time, low transmission fluid can be attributed to one of the following causes:

Transmission Fluid Leak

Much like an engine, transmissions have mating surfaces that rely on seals and gaskets to prevent leaks. As your car ages, these seals can start to leak. A small leak can take a long time to impact the total fluid in the transmission, but eventually the fluid will get low and shifting can be affected. Larger leaks can result in an immediate change, and may leave a puddle of reddish brown transmission fluid under your car. 

Natural Fluid Evaporation

Over time, fluid will naturally evaporate. Generally speaking, the rate of evaporation will be low, but it is still a factor

Wrong Fluid Levels

If you recently had a transmission service performed and notice changes in shifting, it could be a result of incorrect fluid levels. If the technician servicing your car failed to properly fill the gearbox, it may be operating with less fluid than it needs. 

Dirty/Old Transmission Fluid

Transmission fluid provides the hydraulic pressure needed to initiate gear changes. The frictional properties of the fluid are finite, and will degrade over time. Age and contaminants will both impact the effectiveness of the fluid. 

The color and smell of the fluid itself can be indicative of its condition. Old or dirty fluid will be brown or black and may have a burnt smell, while new fluid will be bright red and smell similar to synthetic engine oil. 

Just like engine oil, transmission fluid has a lifespan. When the fluid gets old, you can start to notice more abrupt, rough gear changes. Staying on top of transmission service intervals can help keep your transmission working like it should, and improve its longevity. 

TCU, Sensor, and Internal Issues

Sometimes, the cause of a hard shifting transmission isn’t a result of issues with the fluid. Modern vehicles utilize a range of sensors and computers to control just about everything that happens while you drive, and the sensitive mechanical systems inside modern automatic transmissions can become blocked or fail. 

Valve Body Issues

Inside an automatic transmission, the flow of fluid is controlled by the valve body, a maze of passages that directs fluid where it’s needed. Any blockages or debris in the valve body can result in changes in shift behavior, including hard shifts. 

Transmission Control Unit (TCU) Adaptations

The transmission control unit (TCU) can compensate for a lot of factors while you drive, but may reach a point (if there’s another issue in the gearbox), where it is unable to adapt any further. Resetting adaptations can serve as a bandaid, temporarily improving shift quality until the cause can be identified. An “overnight” change in how your car shifts can be attributed to the TCU being unable to accommodate a problem any further. 

Transmission Diagnosis and Service in Tucson, Phoenix, and Mesa Arizona

If you’re experiencing rough shifting, don’t wait to get your car looked at. The issue could get worse, and may lead to permanent and expensive damage to your transmission. Bring your car to Borst Automotive, and let our teams of expert technicians get to the bottom of the problem. With locations in Tucson, Phoenix, and Mesa, we are conveniently located around Arizona, meaning quality transmission service is just a short drive away. Call or schedule an appointment online today!