Power Pullers --The Ultimate Tow Test: Part Three

Hill Climb Testing

Mike LevineMar 10, 2008
The flat asphalt strip at Milan Dragway was perfect for testing loaded and unloaded level-ground acceleration, but where a heavy duty pickup truly earns its keep is how well it performs climbing hills hauling and towing.
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There were two ways we could have performed the grade testing of the seven gasoline and diesel trucks in our test.
The first was to find a challenging 'real-world' steady incline, like the Cajon or Grapevine passes near Los Angeles, or the infamous 12-mile, 7% ascent to the Eisenhower tunnel in Colorado. The second was to run our tests on much shorter, torturous hill climbs at Ford's Proving Grounds in Romeo, Michigan.
We chose Ford's Michigan Proving Grounds (MPG), for several reasons.
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First, we wanted controlled conditions under which we could run repeatable and measurable standardized tests to compare the results of each truck, relative to both itself and the competition. Second, comparative testing on public highways is a crapshoot. There's a high likelihood you'll get stuck behind slower moving traffic and finding an exit to turn around and repeat a test can require several miles and lots of time - which we didn't have. And third, we drove more than 200-miles around the Detroit Metropolitan area, from test site to test site, so we spent a lot of seat time in the trucks loaded and unloaded.
We tested the three-quarter-ton and one-ton trucks on the 7% and 15% grades at MPG pulling 10,500-pound trailers. As mentioned above, you can find 7% grades on public highways but they are few and far between. And consider yourself lucky if you never encounter a 15% monster. Maybe you'll encounter a fifteen-percenter on a two-lane mountain road but certainly not on a major interstate highway.
That still left us with the one-and-a-half-ton Ford F-450. Like we said in Part 1, we asked Ford to prove how capable the F-450 is at towing - so we tested 'Big Dog Daddy' on the 7% and 15% grades, and (hide your children's eyes) a 25% grade pulling a 20,000-pound fifth wheel!
7% Grade Testing
Three-Quarter-Ton 7% Grade Testing
One-Ton 7% Grade Testing

15% Grade Testing
Three-Quarter-Ton 15% Grade Testing
One-Ton 15% Grade Testing

7%, 15%, and 25% Testing - One-and-One-Half-Ton Diesel Pickup
Ford F-450 Super Duty DRW Crew Cab 4x4 Diesel Pickup

More Head-to-head Performance Charts
We had so many head-to-head performance charts between these trucks we didn't know what to do with them. So click here to see them for yourself.

Power Pullers - Wrap-up
Summarizing our results was difficult, because each truck has strengths and features the others can't match - that go beyond pure performance scores.
Three-Quarter-Ton Gas Pickups - 7% Grade With 10,500# Trailer:
To visualize the hill climb routes at Ford's Michigan Proving Grounds picture a single large hill cross-sected at different angles by six two-lane concrete paved roads, with gradients ranging from 7% to 60% (yikes!) and lengths stretching from 60-feet to 2,000-feet.
The 7% test distance was 1,476-feet long, or 450-meters according to our British-sourced Oxford Technical Solutions RT3102 monitoring unit. That's 156-feet more than a quarter-mile, or 1,320-feet.
For all the grade tests, both truck and trailer were positioned on the grade and stationary prior to the start of the run. The tests were performed 'brake-to-accelerator', i.e., foot brake fully depressed with right foot, then lift and fully depress the accelerator pedal in one movement with the same foot. Sufficient distance was provided at the end to slow the rigs down to a safe speed prior to the top of the hill.
A minimum of three runs were carried out in each configuration tested at wide open throttle (WOT), with the fastest run for each truck used in the results.
The shortest time required to cover the 1,476-ft distance determined the best performing truck.

The Results:
Time (seconds)
Distance (Feet) 2007 Dodge Ram 2500 Quad Cab 4x4 3.73 Rear Axle 2008 Ford F-250 Super Duty Crew Cab 4x4 4.30 Rear Axle 2007 GMC Sierra 2500 Crew Cab 4x4 3.73 Rear Axle
164 8.98 8.05 8.79
328 13.49 12.07 12.73
656 20.38 18.4 19.25
984 25.99 23.93 24.96
1312 31.17 29.03 30.06
1476 33.81 31.47 32.45
Speed (miles per hour)
Distance (Feet) 2007 Dodge Ram 2500 Quad Cab 4x4 3.73 Rear Axle 2008 Ford F-250 Super Duty Crew Cab 4x4 4.30 Rear Axle 2007 GMC Sierra 2500 Crew Cab 4x4 3.73 Rear Axle
164 21.2 24.09 23.26
328 27.12 31.64 31.64
656 36.09 38.45 36.42
984 42.18 42.76 41.64
1312 43.46 45.54 46.12
1476 43.9 46.58 47.7

Photo 4/45   |   7% Grade Cumulative Time Over 450-Meters 3/4-Tons With 10500# Trailer
Photo 5/45   |   7% Grade Cumulative Speed Over 450-Meters 3/4-Tons With 10500# Trailer


7% Grade Cumulative Time Over 450-Meters 3/4-Tons With 10500# Trailer
7% Grade Cumulative Speed Over 450-Meters 3/4-Tons With 10500# Trailer
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What a difference adding some gravity made to the contest for the gas pickups. When you look at the performance numbers and truck specs, there's some high drama happening among these haulers in the uphill quarter-mile.
Hauling a 10,500-pound load, the Ford F-250 took full advantage of its Triton V10's stronger, earlier torque peak to sprint off the starting line well ahead of the GMC and Dodge - reaching 50-meters (164-feet) more than half a second before the Sierra and almost a full second ahead of the Ram. The Sierra's gap would probably have been wider if not for its 6-speed 6L90 HD transmission's fast 4.03 first gear, a good foil to the Ford's 4.30 final drive ratio. By 100-meters, even though the Ford still had the lead, both the Sierra and the F-250 were traveling at identical speeds. But as both trucks shifted into third and their transmission gearing became closer to each other (1.55 in the Ford to 1.53 in the GMC) the massive and early torque peak once again proved decisive for the F-250, allowing it to build a bigger lead again at the 200-m mark.
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The Ford kept an edge on speed until 400-m, when the Sierra finally started moving faster than the F-250. But it was too late for this test's distance. The Ford took the race by almost a full second over the GMC, and by more than two seconds over the Ram.
If the distance would have been longer, it's possible the GMC could eventually have caught the Ford. This time, though, brute force beat cog-swapping finesse.
One-Ton Diesel Pickups - 7% Grade With 10,500# Trailer
The same test approach and distance used for the three-quarter-ton gassers was used to grade the performance of the one-ton diesel pickups.
The final numbers speak clearly when it comes to which diesel powertrain performed best during the 7% hill climb, but watching it play out in the time and speed numbers is like witnessing a chess match. The best individual powertrain components and gear ratios can't win unless they all work together seamlessly and strategically.

The Results:
Time (seconds)
Distance (Feet) 2007 Dodge Ram 2500 Quad Cab 4x4 3.73 Rear Axle 2008 Ford F-250 Super Duty Crew Cab 4x4 4.30 Rear Axle 2007 GMC Sierra 2500 Crew Cab 4x4 3.73 Rear Axle
164 6.77 7.58 6.94
328 10.46 11.38 10.51
656 16.49 17.47 16.25
984 21.75 22.9 21.31
1312 26.57 27.89 25.99
1476 28.94 30.29 28.24
Speed (miles per hour)
Distance (Feet) 2007 Dodge Ram 2500 Quad Cab 4x4 3.73 Rear Axle 2008 Ford F-250 Super Duty Crew Cab 4x4 4.30 Rear Axle 2007 GMC Sierra 2500 Crew Cab 4x4 3.73 Rear Axle
164 26.98 25.46 27.63
328 33.64 31.09 34.19
656 40.59 38.03 42.29
984 45.49 41.38 46.35
1312 47.13 43.95 49.3
1476 47.53 45.51 50.49

Photo 8/45   |   7% Grade Cumulative Time Over 450-Meters 1-Tons With 10500# Trailer
Photo 9/45   |   7% Grade Cumulative Speed Over 450-Meters 1-Tons With 10500# Trailer

7% Grade Cumulative Time Over 450-Meters 1-Tons With 10500# Trailer
7% Grade Cumulative Speed Over 450-Meters 1-Tons With 10500# Trailer

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The Ram 3500 took the early lead in the first 50-meters, with its torquey I6 (earliest torque peak out of the three trucks) and 4.10 final drive ratio. But by the time all the trucks gained some momentum shifting into second and third gears, the Silverado 3500's slightly higher power and torque figures - from the Duramax / Allison combo - were transferred to the pavement more efficiently through its 3.73 rear axle. When both trucks shifted into fourth gear, near the top of the hill, the Ram's speed curve flattened out while the Silverado's continued its upward trajectory.
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Most surprising, though, was the Power Stroke's performance in the Ford F-350. Out of the box this truck weighed about 1,000-pounds more than the Dodge or Chevy rigs. Still, we were expecting better off-the-line performance assistance from PSD's dual sequential turbos, which work at both low and high speeds to provide up to a combined 42-psi of boost (versus 20-psi in the uni-turbo Duramax).
In comparison, the variable geometry turbo (VGT) setup in the Ram's Cummins diesel is also meant to provide low and high speed power throughout the RPM range, but instead of using compound spinners like the Power Stroke, it relies on a single turbo paired with a compressor sleeve that slides forward and backwards axially along the turbo shaft to variably change air volume and psi-boost to the engine. The same sleeve is also used to engage the Ram's exhaust brake. It's an elegant solution that tackles two different tasks.
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The Silverado's Duramax variable vane turbo system is downright simple compared to the Ford and Dodge. Its one-piece exhaust turbine relies on a solid shaft to handle the stress of spinning at 120,000-rpm to suck in huge volumes of air as needed.
We think Ford may not be getting quite the bang for the buck out of its dual-turbos that Dodge and GM are getting from their air-compression architectures.
Another area needing a good tweak is the F-350's 5-speed transmission. Its gears don't grow fast enough to leverage the full power and capability of the Power Stroke. Occasionally the stars aligned for the Ford to fully loose the power housed in the PSD. Fourth gear is 1.00:1 on all the trucks, and this was where the Ford made the biggest jump in speed relative to the Dodge and Chevy - gaining more than 1.5-mph in the last 50-m.
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The end result was the Silverado completed its run almost 5-mph (greater than 10%) faster than the F-350 and almost 2.5-mph quicker than the Ram. Wow!
The Duramax lives for climbing hills under load. We'd feel very comfortable calling on its power if we needed to pass slower moving traffic up a long, steep grade.
Three-Quarter-Ton Gas Pickups - 15% Grade With 10,500# Trailer:
The 15% grade was where we separated the men from the boys. Inclinations this steep expose even the slightest powertrain and platform weaknesses. And there was almost no time for a truck to recover and mask any shortcomings in its powertrain during the brief 820-foot run.

The Results:
Time (seconds)
Distance (Feet) 2007 Dodge Ram 2500 Quad Cab 4x4 3.73 Rear Axle 2008 Ford F-250 Super Duty Crew Cab 4x4 4.30 Rear Axle 2007 GMC Sierra 2500 Crew Cab 4x4 3.73 Rear Axle
164 12.73 11.14 12.38
328 19.93 17.25 20.04
492 26.51 22.46 26.05
656 32.78 27.16 31.02
820 38.93 31.53 35.55
Speed (miles per hour)
Distance (Feet) 2007 Dodge Ram 2500 Quad Cab 4x4 3.73 Rear Axle 2008 Ford F-250 Super Duty Crew Cab 4x4 4.30 Rear Axle 2007 GMC Sierra 2500 Crew Cab 4x4 3.73 Rear Axle
164 14.3 16.61 12.27
328 16.66 20.45 16.38
492 17.7 23.01 19.81
656 18.19 25.14 23.97
820 18.36 26.93 28.23

Photo 14/45   |   15% Grade Cumulative Time Over 250-Meters 3/4-Tons With 10500# Trailer
Photo 15/45   |   15% Grade Cumulative Speed Over 250-Meters 3/4-Tons With 10500# Trailer

15% Grade Cumulative Time Over 250-Meters 3/4-Tons With 10500# Trailer
15% Grade Cumulative Speed Over 250-Meters 3/4-Tons With 10500# Trailer
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The V10 powered F-250's time was even better during the 15% incline than the 7% hill, relative to the Sierra and Ram times in the same tests. The 4.30 rear was a huge help, but the V10's monster torque was also required to get off to a dominant 16.61-mph start in the first 50-m. Ford's gas engine team should be very proud of how this truck performed on such a radical slope.
The Sierra also performed well, though we wondered how much closer or different the results would have been if the old 8.1-liter big block V8 was still available for the GMT900 heavy dutys.
The Ram? Whoa! It fell flat in this contest. In first gear the 5.7-liter HEMI V8 got off to a good start, neck and neck with the 6.0-liter Vortec Max in the GMC, but as soon as the HEMI shifted into that tall 1.67:1 second gear (that we first mentioned during the level 1/4-mile hauling tests) the truck could only lug its way up the rest of the hill. It was a graphic example of how a single mismatch in components caused a giant stumble in performance during this stress test.
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One-Ton Diesel Pickups - 15% Grade with 10,500# Trailer:
After witnessing the dramatic results of the 15% contest among the gas trucks, we were even more interested to see what changes or stumbles might await the diesels on this steep hill.

The Results:
Time (seconds)
Distance (Feet) 2007 Dodge Ram 2500 Quad Cab 4x4 3.73 Rear Axle 2008 Ford F-250 Super Duty Crew Cab 4x4 4.30 Rear Axle 2007 GMC Sierra 2500 Crew Cab 4x4 3.73 Rear Axle
164 8.66 9.2 8.64
328 13.49 14.03 13.07
492 17.95 18.39 16.98
656 22.3 22.59 20.69
820 26.55 26.75 24.28
Speed (miles per hour)
Distance (Feet) 2007 Dodge Ram 2500 Quad Cab 4x4 3.73 Rear Axle 2008 Ford F-250 Super Duty Crew Cab 4x4 4.30 Rear Axle 2007 GMC Sierra 2500 Crew Cab 4x4 3.73 Rear Axle
164 20.98 20.73 22.87
328 24.84 24.85 27.43
492 25.39 25.64 29.79
656 25.96 26.22 30.79
820 26.79 26.43 31.97

Photo 21/45   |   15% Grade Cumulative Time Over 250-Meters 1-Tons With 10500# Trailer
Photo 22/45   |   15% Grade Cumulative Speed Over 450-Meters 1-Tons With 10500# Trailer

15% Grade Cumulative Time Over 250-Meters 1-Tons With 10500# Trailer
15% Grade Cumulative Speed Over 450-Meters 1-Tons With 10500# Trailer

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If we were directing marketing for GM, here's how we'd pitch its diesel motor. D for Duramax. D for dominant. Check out the how fast the Chevy finished the hill climb - more than 5-mph faster and over 2 seconds quicker than either the Ford or Dodge haulers! This time it even beat the Cummins in the first 50-meters.
Though the Power Stroke was still slower than the Cummins to the top, the gap between those two engines narrowed substantially on the 15% grade, in favor of the Ford. If the F-350 and Ram 3500 both had 3.73 rear gear ratios, instead of the Ram's 4.10, we think the F-350 almost certainly would have moved into the second spot.
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But there was an incredibly interesting reason why the performance gap between the F-350 and Ram 3500 seemed to close so much. After two sprints up the hill, the F-350's diesel particulate filter (DPF) went into regeneration mode. The DPF is a new emissions control device required to reduce diesel particulate emissions 10-fold from 2006 model year levels. Regeneration is triggered when the truck senses too much back pressure from the DPF, because of a large amount of trapped particulates. To get rid of the soot, the engine injects metered amounts of diesel fuel into the exhaust stream to incinerate the soot in the filter. On the third run, after regenerating, the F-350 ran the hill up to a full 2-kilometers-per-hour (1.2-miles-per-hour) faster than its first two passes.
We were very surprised by the apparent power boost the Power Stroke received from regeneration. It illustrated just how much the new DPFs can restrict airflow through the exhaust system, and the challenge faced by all the OEMs to improve engine performance while complying with new emissions regulations.
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One-and-One-Half-Ton Diesel Pickup - 7%, 15%, and 25% Grades W/20,000# Trailer
You've read about the 7% and 15% grades, but there was one truck we really wanted to stress test and Ford was more than willing to oblige by lending us MPG's 25% grade. Read on to see how well the Ford F-450 did towing 10-tons of spare parts up a hill most would find difficult to walk.
We know some folks who would be hard pressed to run 100-meters in 17.36-seconds on level ground, let alone up a 25% grade. But the mighty Ford F-450 was able to move a GCWR of almost 30,000-pounds in that time up this insanely steep inclination.
It was a demonstration of pure, gratuitous, triple axle-rated towing capability.

The Results: Ford F-450 Super Duty Crew Cab 4x4 DRW 5-speed auto 4.88
7% Grade with 20,000-lb Trailer
Distance (Feet) Time (sec) Speed (mph)
164 8.16 23.63
328 12.94 28.95
656 19.6 34.09
984 26 36.28
1312 32.07 37.95
1476 35 38.75
15% Grade with 20,000-lb Trailer
Distance (Feet) Time (sec) Speed (mph)
164 9.19 18.55
328 14.8 21.17
492 19.99 22.17
656 25.03 22.51
820 30 22.69
25% Grade with 20,000-lb Trailer
Distance (Feet) Time (sec) Speed (mph)
82 6.24 15.62
164 9.79 15.48
328 17.36 16.15

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More Head-to-head Performance Charts
15% Grade Cumulative Time & Speed for 3/4-Tons and 1-Ton Trucks
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7% Grade Cumulative Time & Speed for 3/4-Tons and 1-Ton Trucks
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Wrap-up Summary:
We're immensely thankful to the manufacturers that supported us in putting together this event. We'd also like to thank the very professional and competent consultants from Ricardo Inc. who instrumented all the trucks and certified the test results.
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All of the gas and diesel pickups we tested are amazing vehicles - worlds better in performance and capability then their predecessors were less than 10 years ago.
Summarizing our results was difficult, because each truck has strengths and features the others can't match - that go beyond pure performance scores. We'd tow and haul with any one of them on a regular basis and would be proud to own and drive all of these rigs.
But we know at least some of you are curious about which gas and diesel truck we'd select if we were in the market for a hard working hauler.
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Out of the three-quarter-ton trucks we'd go with the Ford F-250 V10 Triton. It may not be the quickest performer on the flats but if you need a solid, proven powertrain that can pull hard in the hills with diesel-like performance, this is the truck for you.
We think the one-tons are an easier decision. We'd park the Chevrolet Silverado 3500 and its Duramax in our driveway tomorrow and not give it a second thought. For our reasons why, just read the results below and our assessments from each test.
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And the Ford F-450? It's in a class all its own. With the form factor of heavy duty pickup and the towing power of a medium duty, this is one bad-to-the-bone pickup that begs to be used for towing and hauling only the biggest payloads. We think this is the first of new class of one-and-one-half-ton trucks we'll also be testing from Dodge and GM next time we do the Power Pull Tow Test.

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