>is the total lenght of a c and d unit the same {bumper to
>bumper}?
That depends on how the truck is built. Some C-unit owners spec a short box with a standard sleeper and end up with a shorter truck as a result. Others spec a short box and use the remaining space to increase sleeper size, thereby bringing the truck into the 40-feet-long range, same as D-units. Truck weight will be affected by truck brand (some makes are heavier than others), class (class 8 trucks are heavier than class 7), whether or not the truck is reefer-equipped, fuel tank size, the amount of gear drivers pack into the truck, and other factors that can add up.