A delayed, jerky shift in your TANK 300 is often fluid, valve-body, sensor, or software related.
Here is what to check first and when to stop driving.
Start with the basics: fluid and fault codes
If your TANK 300 feels like it pauses, flares, or jerks as it moves between gears, don’t panic—but don’t ignore it either. On these 8-speed automatics, the first things I check are transmission fluid level and condition, followed by a full scan of the transmission control module for stored or pending codes. Low fluid, burned fluid, or a contaminated valve body can cause exactly the delayed, jerky engagement you are describing. A proper scan tool can also show whether the transmission is in limp mode, whether shift adaptives are out of range, and whether there is a software calibration update available.
Next, look at live data rather than guessing. Input and output shaft speed sensors, the transmission range sensor, throttle pedal position sensor, and temperature readings all feed the shift strategy. If one sensor is lazy or intermittent, the TCM may command a shift late or with the wrong pressure, which feels like slipping. Also check battery voltage and grounds—modern transmissions are sensitive to voltage drops—and inspect the wiring and connectors at the transmission for corrosion or chafing. If the fluid is clean and the codes point to pressure control, the valve body and its solenoids are common suspects.
