DETROIT — Six years ago, Ford made a Texas-size wager on the top-selling vehicle in America, rolling out a radical new version of the F-Series pickup with a lighter aluminum body instead of the customary steel.

Now it’s time for another revamp, and Ford is playing it safe with the company’s crown jewel.

On the outside, the truck changes little, and the internal combustion engines and transmissions remain the same. The biggest differences are a gas-electric hybrid version, internet connectivity, and a revamped interior that turns the truck into more of a rolling office or even a place to nap.

There’s good reason for Ford to minimize changes. Since the 2014 revamp, it has sold nearly 4.5 million of the aluminum-clad trucks, holding its sales crown despite challenges from Chevrolet and Ram. Pickups also have been a bright spot during the pandemic as automakers cautiously restarted factories last month.

Annette Sykora, who runs Smith South Plains Ford in Levelland, Texas, said Ford’s conservative stance is smart. “It’s been the No. 1 seller for a number of years, and a good, tough truck that does the work,” she said. “We definitely don’t want them to mess with that.”

F-Series pickups are so important to Ford that a mistake could cost the company at a critical time with a wobbly economy due to the coronavirus, restructuring costs and investment in new technologies draining badly needed cash.

The big pickups generate $50 billion per year in global revenue, about one-third of what Ford normally takes in. That’s more than revenue generated by entire companies such as Coca Cola or Delta Air Lines. The F-Series brings in $42 billion in U.S. revenue, raising more cash than every other consumer product except the iPhone, according to Boston Consulting Group.

In Texas, where more pickups are sold than any other state, one in every five new vehicles sold is a full-size pickup. It’s one in every seven nationwide, according to Ford research.

“There’s really nothing more important to us than the F-Series,” Ford CEO Jim Hackett said in an interview. The aluminum body, he said, gives the trucks an advantage in handling over competitors that will carry over into the new version, he said.

Sam Pack, who owns four Dallas-area Ford dealerships, says the F-Series accounts for well over 40% of his sales. Company research pointed toward revamping interiors to make it easier to do office work in the cab, said Pack, one of the dealers who advises Ford on new vehicles.