[Douglas]

There's something I've been wondering about Peterbilt trucks.

1. It seems like all the trucks with the more powerful engines (over 500 hp) are box model trucks.

and not the round model.

2. Why is it that when I'm going down the road, the box model peterbilts are louder than h*ll?

[boneebone]

Because it's like driving a building through the wind, no aerodynamics to it.

You can spec. any make, model truck with any engine you want, depends what your needs are.

These days with the price of fuel, aerodynamics and fuel economy are more important to companies and most O/OPs.

The most expensive cost in trucking is fuel.

Alot of Pete owners put unmuffled straight exhaust pipes on the trucks, hence the loudness.

[Uturn2001]

Most trucking companies, regardless of make and model of truck, tend to spec the trucks with engines between 435 and 475 hp. A lot of this has to do with fuel economy.

As mentioned before, when a truck is ordered, it can be done so with practically any HP engine you want as well as rear end and tranny combo that will work with that engine.

[Ironturkey]

I used to drive a 379EXHD with a 475 cummins and a 13spd and I averaged 6.8 to 7.5mpg loaded to the knats ass with pork bellies

[PackRatTDI]

One of our local dump trucks is a nice narrow window Peterbilt 359.