191-160-89-I17-169
Skip the 163 that rgatijnet posted if you want fastest (not shortest). Its a little longer distance wise but pretty flat, less hills, less curves and less traffic. However the route with 163 has Monument Valley and if you never seen it I would go that route.
...and expect traffic delays in Cameron, AZ. I also like to fuel up in White Mesa, UT, nice station with lots of room for RV. Keyenta is over priced and Tuba City is ok.
BTW, have you ever used google maps?