Q: Why does the truck shake while driving?

Hi there. Sounds as the engine is misfiring and is not running on all cylinders. Check the spark plugs and wires on the engine and see if any of them are crossed or shorting to ground. I recommend replacing the spark plugs and wires if they are more than 5 years old. Check the fuel system and see if a fuel injector is not firing. While the engine is running, unplug one fuel injector at a time. This will determine if the injector was indeed working. Even if the spark plug was not firing, the engine will try to stumble a little more than normal. If you unplug a fuel injector and there is no change to the engine, then the injector was not working. I recommend conducting a fuel injection treatment before replacing any fuel injectors. If you need further assistance with your engine misfiring, then seek out a professional, such as one from Your Mechanic, to help you.