More than half of American commercial heavy trucks are six to nine years old or more and seemingly ripe for replacement, according to a survey of fleet executives by Newport Business Media.

Of 294 respondents answering a question about truck age, 40.8% said their trucks were six to eight years old and another 18.4% said they were nine years old or more. One-third (33.3%) said their trucks are three to five years old and 7.5% gave their vehicles' age as less than three years.

In ordering components for new trucks, 92% said the engine was the first decision made, followed by the transmission (78%), chassis (73.8%) and axles (50%). Only 27% said a truck's electronics were among the first decisions, but 73% said electronic parts were important as a secondary consideration.

Previous experience with components was by far the most important consideration in making decisions on specifications, respondents said. For transmissions, 80.8% said experience with products was important, followed by 78.5% for axles, 71.8% for chassis, 71.5% for engines and 65.2% for electronics.

The survey was sent to 10,000 managers of Class 8 fleets that are subscribers to Heavy Duty Trucking.