what size engine?
Timing chains don't need to be changed. And if they break the engine will shut down. But my mechanic said they're almost never changed
If eng is 4.9 in line 6cyl it,s gears,V8,s have timing chains. In regards to replacing timing chains as a maint item, it depends on make,model and engine. Some vehicles will bend the valves or worse if a chain or gear fails. This applies to timing belts as well.
Search Ford F-150 Questions
Ford F-150 Experts