Transmission shudders seem worse than they actually are. Shudders occur most often when shifting into overdrive or when in overdrive and going up a slight incline. This occurs because the transmission fluid is contaminated and the contaminates, being suspended in the fluid, prohibit good pressure contact between the transmission plates when they are applied. Routinely servicing the transmission prevents this from occurring. Left unserviced, the condition will worsen.
Jack up the front of the car and install jack stands under the frame. Lower the car and make sure it is securely positioned on the stands.