Here are some factors that can affect driving time:
* Traffic: Traffic can be heavy on Interstate 40, especially during peak travel times such as summer weekends.
* Road conditions: The road conditions can be challenging, especially in winter weather.
* Stops: You may want to make stops along the way to rest, eat, or sightsee.
If you are planning to drive from Pasadena to the Grand Canyon, it is important to allow plenty of time for your trip. You should also be prepared for challenging driving conditions, especially in winter weather.