Wow, are you brave. I wouldn't chance the Sonora Pass with a trailer. It's far and away the steepest and most challenging Sierra pass in the Eastbound direction. With our 1990 VW Camper, we barely make 10 mph over the crest, but worst, the brakes always fade on the way down. Scary stuff.
Glad you made it safely. Hope others don't think that this is a wise route, however.
Mike Young & Rosemary Nelson
Bowlus Road Chief "Endymion" (coming soon)
BMW X3 xDrive 28D