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