3 2008 Ford Super Dutys Get Fuel Economy Improvements
By: Mike Levine Posted:
01-02-08 11:30 PT
© 2008 PickupTruck.com
to refine the 2008 F-Series Super Duty. Only a few months after
Job 2 trucks started
rolling off the assembly line, Job 3 pickups are ready to go with changes
aimed at improving fuel economy, without compromising capability.
replacing standard 3.73 ratio rear axles on certain F-250 and F-350
Super Dutys with 3.55 running gear and has lengthened the
underbody chin spoiler by 100-mm (3.93-in).
spokesperson Wes Sherwood says, "We are making the 3.55 standard and
when that's combined with new front-end aerodynamic improvements, there
will be about a 1.5 miles-per-gallon improvement."
to quantify the fuel economy improvement in percentage terms because
three-quarter and one-ton heavy duty pickups aren't
required to carry EPA mileage ratings. But this could mean as much
as a 10 to 15-percent improvement for some drivers, depending on how
they use their truck.
for those who frequently tow: Mr. Sherwood says there will be no decrease
in capability. Super Dutys with 3.55 rear axles will still tow the
same as earlier Job 1 and Job 2 3.73 equipped trucks.
cab 5.4-liter Triton V8 gasoline F-250 and F-350 single rear wheel
trucks, max towing remains 9,100-lbs and for regular cab 6.4-liter
Power Stroke V8 diesel F-250 and F-350 single rear wheel trucks, max
towing remains 12,500-lbs.
why this is important, it helps to understand how rear axles are rated. Rear
axles are assigned numbers that describe how many rotations the driveshaft
must make to turn the rear axle (and rear wheels) once. A 3.55 rated
rear axle turns the wheels once for every 3.55 driveshaft rotations.
axle ratio can make a big difference in towing performance. The higher
the ratio, the faster the driveshaft turns and the sooner the driveshaft
can transfer peak horsepower and torque from the engine to the rear
wheels. The result, generally, is faster acceleration and higher towing
capacity than a rear axle with a lower ratio. The tradeoff for a higher
axle ratio, though, is usually lower fuel economy, because an engine
that's working harder is also burning fuel faster.
But in the
case of the newly standard 3.55 rear axle, Ford isn't compromising
on towing performance while it gives drivers higher fuel economy numbers.
However, it's likely that 0 to 60 performance, particularly while towing,
will drop with the move to the lower rear axle.
summary of Job 3 rear axle changes across the Super Duty lineup:
rear wheel (SRW) F-250 and SRW F-350 Super Dutys with 5.4-liter Triton
gas V8 engines receive standard 3.73 ratio non-limited slip differential
rear axles that replace previous 4.10 ratio non-limited slip
diff rear axles. Expected fuel economy improvement of 0.5-mpg.
F-250 and SRW and dual rear wheel (DRW) F-350 Super Dutys with 6.8-liter
Triton gas V10 engines receive standard 4.10 ratio limited slip rear
diff axles that replace previous 4.10 ratio non-limited slip diff
rear axles. No change in fuel economy.
- SRW F-250
and SRW F-350 Super Dutys with standard 17-inch and 18-inch wheels
and automatic 6.4-liter Power Stroke diesel V8 engines receive standard
3.55 ratio non-limited slip rear diff axles that replace previous
3.73 ratio non-limited slip diff rear axles. Expected fuel economy
improvement of 1.5-mpg.
- SRW F-250
and SRW F-350 Super Dutys with optional 20-inch wheels and manual
or automatic 6.4-liter Power Stroke diesel V8 engines receive standard
3.73 ratio limited slip diff rear axles that replace previous 3.73
ratio non-limited slip diff rear axles. No expected fuel economy
- DRW F-350
Super Dutys with 6.4-liter Power Stroke diesel V8 engines receive
standard 3.73 ratio non-limited slip diff rear axles that replace
previous 4.10 ratio non-limited slip diff rear axles. No expected
fuel economy improvement.
these changes are being made at this time, Mr. Sherwood says, "Ford
is constantly looking to innovate with its trucks. Fuel economy is
on people's minds right now and we're not going to wait until the next
model year to make a change. We're going to implement changes like
this as soon as we can."