My car has an automatic transmission. I have a problem with the truck shaking at times when I drive steadily at about 40 kmph. At times, it feels as though it has a manual transmission and as if I didn't pressed the clutch--like it is going to die out completely. Therefore, I have to do either downshift to D3 or press the overdrive so that it stops shaking. Other than this, the vehicle runs fine. Do you have any suggestions?
Erratic shifting into gears too early will cause overloading of the engine and the shaking you feel. An engine that misfires under load may miss when at this speed before shifting into overdrive. If the transmission is shifting into overdrive before 40 mph then the vehicle speed sensor or transmission input speed sensor may be giving incorrect readings. Have the engine mounts checked to make sure there is no corrosion or pin and socket problems. A certified mobile mechanic can inspect and diagnose what’s causing your truck to shake.