What's the difference

[ajpag]

Specing a new truck for a new business venture.
C5500 Chevy. The up fitter offers the 210 HP
and the 300 HP 6.6. Of course at differnt prices.
He tells me that the 210 gets better mileage?
They both have the same tourque spec's so what
gives. I could go with the 210 I guess and install
a programer so if I want more power, I could crank
it up. Also, the 210 is set up with the 1000 Allison and the 300 with a 2200. You would think
that with a lower gear in the 2200 it would be the
other way around. Rear end gear is 4.88 or 5.13.
Likely go with the 88's with 2.25's on 19.5's. Opinions and advice please...

[More Power]

In addition to different power specs, they also may have different engine governed rpm limits (i.e. 2700). This should be factored into the calculated highway speed and engine rpm ranges.

Does the Allison have the sixth gear? This may also play into the gearing/rpm equation.

Generally, best fuel economy comes when the engine is at its torque peak (about 1600-1800) for your chosen highway speed. Up to ~2000 rpm should be OK for best fuel economy.

Jim

[ajpag]

Jim, the allison in this model is the 5 speed. I
finally got the GM specs today from the up fitter.
I don't feel comfortable with the speced truck they use as "their standard chassis" so I'm specing exactly what I want. Dealer is telling me
that it will delay everything but thats ok. Looks like I can save a few bucks going with the 210 HP
motor and if I spec the 8000# front and at least
the 15000# rear, I'll be able to order the 2200
allison. Also, then you move up to 4 piston rear
calipers. Whew - Have to really read between the lines on all these spec's and it does pay to ask questions. Thanks again for the advive... Anthony.

[markrinker]

FYI: My local dealer said the 6-speed Allison will not be offered in 4500 or 5500 series trucks.

[mdadgar]

He tells me that the 210 gets better mileage?
They both have the same tourque spec's so what
gives. If the torque is the same and the HP is different, then the likely delta is the rev limit. They are setting the redline artificially low to limit HP.

That would also produce better mileage, all else being equal.

- Mark