Good Morning Ford Dudes,

Learned something today. I have a 2011 F550 4 door dually 4WD cab chassis which of course has the straight frame instead of the pick box frame. What I didn't know is the the Cab Chassis has 100 HP less than the pickup body same diesel engine and tranny. Anyone know why that is and if it can be changed without putting a chip in?

Bill J

 

I have the exact same rig (hence, the "W57" VIN code in my user name), only mine is much older (hence, the "Y2K".) But I try to keep up with the changes as they evolve.

The issue here is that the 6.7 Scorpion motor in the chassis cab is plumbed differently than the pickup. The chassis cab has an entirely different turbo... which unfortunately has been more prone to failure than the turbo system in the pickups, as reported by Ford service technicians in the field and customers alike.

Naturally, the different turbo will have different plumbing. And the PCM will have different calibrations, but that has always been the case with the chassis cabs.

Note that the chassis cabs have much larger drive axles. While the pickups have 10.5" corporate Ford aka Sterling, and some F450's have an 11.2" Dana 80, your F-550 probably has an 11.8" Dana 110 (or in rare cases a 12.2" Dana 130 if your rig has the 19,500 GVWR pkg). My older F-550 has a 14.2" Dana 135 (hence my avatar, which signifies that I'm usually talking out of my rear end, so keep that in mind). These are medium duty drive axles, and Dana specifies input horsepower limitations on them to maintain their higher axle capacity ratings.

Specifically, Dana's input horsepower limitation for the Dana S14-110 (aka Dana 110) and the Dana S16-130 (aka Dana 130) is 310 horsepower and 600 ft lbs of torque. Ford's flywheel horsepower rating is already 330 HP and 660 FtLbs on the chassis cab. (Reference Source: http://www2.dana.com/pdf/AXSL-0052.pdf )

Note that when Ford announced the new 440 HP and 860 ft lbs of TQ ratings for the updated 2015 6.7 engine in the forthcoming 2015 pickups (with yet a different turbocharger), these new ratings do not apply to the 2015 chassis cabs, whose engine HP ratings remain unchanged.

 

Thanks Y2KW57

That was a bunch of info I didn't have. If I get your point it is that the rear end has a limit to the torque it can take due to the wider wheel track axle and GVRW. So...if it ain't broke don't screw with it because it's gonna break. )

 

You're welcome. Thank you for the personal risks you take protecting your community.


No, that isn't my point at all. I didn't say anything about "wider wheel track". In this case, axle width has nothing to do with the input HP rating. In fact, the F-350 pickup trucks with 440 HP have a wider rear axle wheel track, at 94.7", than the 330 HP chassis cab rear axle dually wheel track, at only 93.6". This is due to the wider frame width of the pickups, at 37", over the chassis cabs, at 34".

My point is that the axle manufacturer (Dana) has established an input HP restriction on the medium duty axles to maintain their reliability at their given weight ratings. This could be related to any number of things in the construction of the axle, but it does not automatically follow that wheel track width is of any consequence whatsoever, as has been proven with the wider width of the lighter duty dually pickup axle.


On this point I fully agree. Especially if we are talking about a fire apparatus in public service that is still potentially under factory warranty, as fire trucks generally do not accumulate that many miles, and it being a 2011, is still less than 5 years old. Concerns about reliability as well as liability in a rescue vehicle would give me pause as well.