Ford, Chevy, GMC, Daimler dealers are franchised as car dealerships, truck dealerships, or both. Car dealerships can sell and service passenger cars, small trucks, and vans. Truck dealerships sell trucks only, and are equipped to service large trucks.
Cities 200,000 to 500,000 will usually have one truck dealership each manufacturer, Ford, GM, Daimler (Chrysler got out of the medium and heavy truck business under the terms of the first Federal bailout in the 70s).
The first will always be a Ford dealer, the second used to be either GMC or Chevy, now tend to be combined Chevy/GMC (and might also be a truck service center for other brands). The dealer handling Daimler trucks, whatever brand, will usually be a Freightliner center in the U.S., although a select M-B dealer might service the Sprinter only, but not necessarily motorhomes built on M-B Sprinter chassis.
Larger Metro areas may have multiple truck dealerships, in the proportion one for every 5-10 locations for car dealerships. Most will be on the fringes of the area, one of more of the suburbs or bedroom communities.
Where all the dealerships have one owner, the service consultants are usually pretty quick to direct you to the location of their truck service center. Where a competing dealer owns the truck center, the service guy may not be so helpful.
In rural areas, smaller dealers in small cities 50-200 miles from the nearest metro area will usually be combined car and truck dealers, might even have franchises for multiple brands crossing manufacturer lines. In rural areas, a quarter to half of sales will be larger trucks, but sales are not enough to support separate truck dealerships.
My small town Ford dealer sells medium-duty trucks and will service RVs (even those on GM chassis). They can handle an oil change by pulling partly into one of the Quick Change bays, but for any more work, an appointment is needed, because they have only one truck size bay, and some jobs can tie that up for a day or even several days.
For your Class 4, 5, 6 truck, what your motorhome is to a car or truck dealer, find the truck dealership.
