The transmission is not shifting into the highest gears, and driving 70 mph like that is going to cause engine damage. You're going to need a mechanic to interpret that shaking. There's no way I can tell if that's the cause of a problem or the result.
One thing you can try is to stop on a slight incline, shift to neutral, release the brakes, then see if the car creeps downhill on its own. If it doesn't, a brake may be dragging. That will cause you to have to push the accelerator pedal further than normal, and the transmission would interpret that as hard acceleration or going up a steep hill. With either of those conditions the transmission would want to stay in a lower gear. You'll find a dragging brake too by feeling the wheels after driving a few miles. One wheel will feel a little warm, and the wheel by a dragging brake will be much hotter.
If the brakes are okay, you could also have a transmission problem. If it's computer-controlled, an electrical issue can keep it from shifting properly. For those, the place to start is by having the diagnostic fault codes read and recorded. When electrically-controlled transmissions get stuck in a lower gear and stay there, that is a default that allows you to drive slowly to a repair shop without needing a tow truck, but definitely not 70 mph. The clue to this is it is usually necessary to turn the ignition switch off, then restart the engine to reset the computer. At that point you can watch if proper shifting occurs, and at what point it stops shifting normally. That is an important clue to the mechanic.
Monday, April 27th, 2015 AT 10:23 PM