specking a new truck

[Hammerhead]

The X15 is basically an unknown quantity at this time. Based on Cummin's so called improvements with the 2250, then the 2350, I'm not willing to make a prediction at this time.

I agree with Brock on the gearing as well as the suspension.

The gearing having you run at 1600ish RPM is going to help you by creating airflow through the emission system, which for regional and or short haul applications such as yours will help ensure that passive regens get the opportunity to complete efficiently where RPM operations may inhibit good regens.

Neway is a very good Heavy Haul suspension, however Hendrickson's Primax suspension is a true 4 link design. If you were to go to any drag track and talk to them they will all tell you that the 4 link design suspension actually builds traction under power, which for off-road applications is an asset. I decided Primax over Neway in my truck and there have been times where I was sure that I would get stuck and didn't. In full disclosure, I will also assure you that Neway does have a better/softer ride.

Do you really need 46k rear ends? I know Cali allows that kind of weights on tandems under permit, so you very well may. The reason I ask is that a couple of years ago I had a drive wheel seal failure in San Diego, and El Cajon KW didn't have bearings in stock for Eaton 46's! I couldn't believe it with all the HH trucks around Cali, but they told me almost nobody around there runs them. I was fairly skeptical, but that's what the service Dept said, and waiting for parts for diffs is a real pain. I asked about the availability of reman out of curiosity, and he told me 3 days away. Anyhow, something we do in our HH application is we run 46k diffs with 52k suspensions. I know it sounds questionable, but think of this; almost all freight trucks run 40k rears and legal axle weights are 34k. Using an overrated suspension increases longevity and improves ride as you are not at the limit during loaded operation.

As for the front axle, anything over 14,600 and I am absolutely adamant that the truck has dual steering boxes. I know engineering will tell you that one is enough, but it's barely enough. Dual boxes are more stable, reliable, and run much cooler than a single. I did the single on this truck and I regret it. If you are running the big weight on your front end, I think you should seriously consider 385/65R22.5 tires. They do cost more, but if you are consistently running the weight, they will last longer enough to offset the cost. The other side to it is if you are on a soft site long enough you can deliberately under-inflate them allowing them to "spread" the weight across a larger surface area allowing for better control. I drop mine to 70-75psi in these conditions and it helps tremendously.

As far as tires go, you run way longer in warm temps than Brock and I do and it sounds like you've made some astute observations based on your application.