To BobGed, thanks for the link to the map; that's the kind of information we wanted and we'll use it in the future. To smkettner, you are correct, there is no sign about "over 40 prohibited". We would have turned around if there was. There is a sign that says "Not recommended for trucks over 30 feet kingpin to rear axle". We are 22 feet so we fit that.
A note about "truck" signs. In our first year, we were in San Jose trying to get onto the Freeway 85 and the signs said "No truck over 7 tons". We are 13 tons so we did not ever get on the 85 as all entrance signs said the same. We drove surface streets east until we got to the 101 South. Later research with CalTrans informed us that we are not a "truck" and we could have gotten on the 85. We now watch for "vehicles" versus "trucks". But again on this road we were under the recommended maximum regardless of vehicles vs trucks.