The 18 AutoShift can skip gears on its own. I want the split upper gears, and there is not an auto verion of the 13. Their 14 speed performance transmission is full auto, with no clutch, and can only be had up to 1750 ft. pounds, which means uprating the motor is no go. I would consider tolerating the lower torque rating, but not the lack of a manual clutch, since it has the lowest ratio of the 18, doesn't split the rest of the bottom side, and splits the top, which would do all I need.

The idea is to gear for 65-70 at cruise, consistent with the speeds out west, but have the capacity to run in the slower areas without having to drop a full hole as would be needed in a 9-10 speed.

Bubble? No. Escape pod? Yeah. I used to be the legal advisor to the Public Health Department where I worked, and had a lot contact with the concept and consequences.

Doug, I had an 05 Freightliner Century C15,Freedomline, twin screw with 22' box that I used for a mobile service truck. Trans replaced at 13000 miles and front axle was too light....SO
Ordered '07 Century Cat C15 435hp/1650ft lb, Eaton 13 spd, twin screw, 3.58 gears with 22.5 tires and 16000 lb front. Still use the truck for work (although maybe not much longer)and at 33000 lb this baby hauls. There is no replacement for displacement, also watch where the torque peaks-torque pulls the load. With regards to the trans, yes it shifts every gear in "auto" but in manual I can "double click it" and skip shift. I have tried this but eventually go back to auto and let the truck shift itself.
I did a lot more research after the first truck and still think the Freightliner and Caterpillar support network makes it was hard to pick any other combination.
Will probably have a 30'Showhauler conversion installed and pull a 26' enclosed trailer with Jeep and Harley's inside. If I need it tweaked I can go to Cat, pay the additional warranty cost and turn up the power to 475 without affecting the trans warranty.
BTW I worked for the Cat dealership for 29 years, so am just a little partial to yellow iron-are they more expensive to repair? I don't think so, wait and see what the Mercedes costs.
A class 8 truck doesn't have to lift the tag axle like its motorhome sister. On the twin screw, the rear frame is meant to be dragged around corners and haven't heard of one cracking between the axles like the motorhome with tags do.