IdaD wrote:
I'm going to need a source on your 150k lifespan figure or it's made up too.
A heavy duty truck isn't over-designed, but it is designed to haul more and more often (duty cycle). A half ton isn't under-designed, but it is designed with a different purpose. I don't doubt for a second that a heavy duty truck would hold up better at max GCVWR than a half ton at max GCVWR, especially a diesel HD truck.
You could have the exact same discussion about a 2500/3500 versus a chassis cab 4500/5500. Different class, different purpose. This is not a complicated concept.
I posted this a few days ago:
1st of all, 150, 250, vast majority of 350 (non dualies) are not Medium Duty trucks.
https://en.wikipedia.org/wiki/Light_truck
Light duty trucks have payloads less than 4,000 lbs.
The best I've got is the Ecboost torture info here where they say they tested it to 150k:
http://news.pickuptrucks.com/2011/01/what-the-inside-of-a-torture-tested-ecoboost-v-6-looks-like.html
You also need to look no further than the service schedule in your own truck - notice where it stops. That is generally the design life.
Google "Medium Duty Truck" and you'll see they are not a F150, F250, F350. They are your box truck chassis.