A shuddering torque converter is usually caused by using the wrong transmission fluid that does not have enough of a specific additive. To verify that, first be aware the shudder usually only occurs during initial lockup, although my daily driver does it continually, once warmed up, at around 35 mph. You will not feel the shudder below about 30 mph, not unless the transmission is in the highest gears, and not until the engine is warmed up. You should also not feel it at speeds higher than about 50 mph.
When you feel the shudder, hold the accelerator pedal perfectly steady, then lightly tap the brake pedal with your left foot. Doing that initiates an unlock and the shudder will stop for two or three seconds.
A failing torque converter can cause the same symptom, but it is very much less common than using the wrong fluid. A failing torque converter will typically cause shuddering at higher speeds too.
Wednesday, November 30th, 2016 AT 6:07 PM