Category: Transmissions

Common Fixes for a Transmission that Jerks or Hesitates

Here are a few common reasons why your transmission may shift erratically, jerk or hesitate.

• Low fluid level
• Depleted fluid frictional properties
• Poor cold-temperature fluidity

Start with the easiest fix

There’s an old adage when troubleshooting: start with the least expensive and simplest fix. In this case, check the transmission fluid level first. Low fluid can prevent the transmission from shifting properly. It’s important to find out why the fluid is low and fix any problems. It could be a leaky seal or other mechanical defect. Otherwise, adding new fluid won’t ultimately solve the problem.

Worn fluid equals poor shift quality

Transmission fluid that has aged and lost some of its frictional properties can also lead to poor shift quality. When your vehicle’s computer tells the transmission to shift gears, hydraulic pressure (provided by the fluid) squeezes a series of plates together inside a clutch pack to connect the engine to the transmission output shaft and route power to the wheels. The fluid’s frictional properties play a vital role in ensuring the clutch plates bind together properly and gear shifts occur seamlessly. Over time, the frictional properties of the fluid can degrade, leading to elongated, jerky or inconsistent shifts. In this case, it’s time for a fluid change. How do you know for sure the fluid is worn? The only definite way to find out is to conduct used fluid analysis. However, fluid that smells burnt or appears dirty is likely due for a change. It’s best practice to change the fluid before the frictional properties are depleted and poor shifting is experienced since poor shifts can cause the clutches to wear more rapidly and lead to bigger issues that need mechanical repairs.

Be aware of “adaptive” transmissions

One interesting note affects newer vehicles equipped with adaptive transmissions. These units “learn” your driving habits and the characteristics of the fluid to adjust shifts accordingly. As the fluid loses its frictional properties, the computer compensates and adjusts transmission performance. If you’ve recently changed your fluid, the computer may still operate as if old fluid is installed, causing poor shift quality. In these cases, keep driving and eventually the computer will “relearn” your driving habits and the behavior of the new fluid and adjust accordingly. The problem was significant enough on some 2012-2013 Ford F-150s to cause Ford to issue a technical service bulletin (TSB 13-1-10).

Your transmission fluid’s frictional properties are vital to best performance

To demonstrate its outstanding performance, AMSOIL Signature Series Synthetic Automatic Transmission Fluid was tested in taxi cabs operating in the intense heat of Las Vegas. First, the frictional properties of new fluid were tested. Then, after more than 180,000 miles of work in a fleet of taxis, the fluid was tested again. As shown in the graph, the fluid maintained nearly identical frictional properties to new fluid after 180,000 miles of severe service. That translates into solid, confident shifts day after day and long transmission life.

Cold weather can reduce shift quality

When the temperature drops, transmission fluids with poor cold-flow properties can thicken and cause elongated and hard shifts until the fluid has warmed up enough to flow properly. Switching to a high-quality synthetic transmission fluid will help. Synthetics don’t contain waxes, as conventional fluids do, so they remain fluid at lower temperatures for improved shifts during cold weather.

The best transmission fluid available won’t fix a broken transmission. But using high-quality synthetic transmission fluid can help improve shift quality and maximize transmission life.