Ford: 1987 Ford 150 Lariat, ford 150, hoses

Question
My bother just had transmission replaced.Truck runs great transmission works good but begins to idle fast once it gets warmed up.

Answer
Hello,


It sounds like a vac leak.

when the engine idles faster, spray a carb spray around the intake and hoses and listen for changes, hissing, idle changes, runs rough etc.

You dont state if it is automastic, or which engine it is, but a transmission swap generally will not affect idle unless a hose  or wire was pinched or left disconnected, or soemthing else was damaged.

I assume a leak, because some cracks open as the metal gets warm