Pulling a heavy trailer up a steep grade is the truest test of diesel pickup performance. The heavy-duty diesel pickup remains the tool of choice for serious towing duty, and following the trend in diesel pickup performance is the primary focus for The Diesel Page's annual Pull-Off. This year's event marks the fourth time we've evaluated GM's frontline contender in the diesel pickup power wars, in both stock trim and when modified for more power.
Each year, we use the very same grade used for all prior Pull-Off events, and we run each truck exactly the same way. With a 10,000-lb trailer, we launch from a dead stop on a 6% grade, and run from one mile-marker to the next - exactly one mile. Elapsed time and top speed (as measured by a chase truck) are recorded for each run. The importance of these tests is that it accurately measures truck performance - not just engine performance. Rowing through the gears allows us to evaluate the transmission gear ratios, the useable RPM range of the engine, and of course, the engine's ability to produce power over that RPM range. The diesel engine that can produce the most power over the widest RPM range (area under the curve) will win these hill-climbs if matched with suitable gearing.
We were looking forward to running a new Ford 6.0L Powerstroke this time around, but it did not happen. With a horsepower, torque and 700-RPM advantage over the Duramax 6600, I fully expected the new Ford diesel would win in a stock/stock contest. The longer you can stay in a lower gear means your drivetrain will be putting more power to the ground than a competing engine with a lower RPM governed limit. However, just days before the event, the new Ford we had scheduled for the Pull-Off suffered from a severe fuel/oil dilution problem that wiped out the turbocharger. A second truck also experienced the same problem, but the turbocharger failure this time required an engine replacement. No other 2003 Ford owner we contacted would risk his truck for a full-pedal run up the hill with a 10K trailer. Curiously, all 2003 Dodge owners we contacted were similarly reticent. We did have a couple Ford 7.3L PSD and earlier Dodge Cummins trucks run the hill. Pictures and data are included below.
Looking downslope from the finish line, John Kennedy's modified 2002 Chevy 2500HD Crew Cab Duramax/Allison was churning 75-mph at this point in the run. At 17,400-lbs combination weight, the big Chevy accelerated hard all the way through the 1-mile course. A balky Allison hampered JK's truck somewhat this year, but no one could better his class-winning 75-mph top-speed.
Even when running at this weight, this modified Chevy still has an impressive acceleration. Scott Eckerson recorded top speed for every run using his 5.3L Vortec equipped 2002 Chevy K1500. Scott said keeping up with Kennedy required full-throttle just to maintain following distance. We may need a faster chase truck next year!
(BassinRVer) was eager to see what his 2002 Chevy would do on the hill. The performance upgrades Robert added helped push his lifted Chevy to a top speed of 66-mph and an elapsed time of just 1-minute and 3-seconds.
Jeff VanHelden's 2002 Ford F350 SuperDuty Powerstroke was a strong runner, producing a 55-mph top speed in just 1-minute and 12-seconds. Besides having a 9-year history of success, the 7.3L Navistar engine continues to prove itself a capable performer in real-world performance tests like these.
Willy Wagner's 1995 Dodge 12-valve Cummins was running with an aftermarket P7100 fuel plate and other "unmentioned" performance mods. Whatever combination of products he had, they allowed his Dodge Cummins to attain 68-mph in 1-minute and 5-seconds at the 1-mile point in the run.
Darrell Moudry's (Motovet) juiced-up 2002 Chevy attained the second highest performance run of 70-mph, in just 1-minute and 1-second. Darrell ran later in the schedule, and knew whom he had to beat. Competition has a way of pushing the EGT limits we all normally set for ourselves. No fear here!
Pat Storer (SS396) volunteered his totally stock 2003 Chevy 2500HD Duramax/Allison to test the theory some have about all 2003 models being "down on power".
Pat's 2003 Chevy produced a top speed of 55-mph and an elapsed time of 1-minute and 14-seconds. Just like the protoype Chevy we tested in October of 1999, a 2001 GMC we ran in June of 2001, a 2003 GMC 2500HD we ran last fall, as well as a host of other '01 & '02 models, Pat's Chevy proved once again that the 2003's perform almost exactly the same as all other stock Duramax/Allison equipped trucks we've tested.
Jerry Heggerston's 2001 Chevy 3500 HD 8.1L/Allison gave us an opportunity to answer the question some have about whether the Duramax 6600 or the 8.1L Vortec has an all-out performance edge in these sorts of contests. Just like all other tests, Jerry's truck and 10,000-lb trailer launched from a standing start on a 6% grade, and ran full-throttle for exactly one mile. His 4.10 rear differential gearing and much wider useable engine RPM range should have (in theory) given his truck an edge... However, the chase truck's speedometer (same one used for every run) and stopwatch showed a top speed of 53-mph in 1-minute and 17-seconds.
A 4.10 geared 8.1L does a really fine job, but it is not faster than a stock 2500HD/3500 truck equipped with a Duramax 6600 and 3.73 gears.
Representing the 6.5 crowd, Ken Hessler ran his 1992 6.5TD GMC up the hill with the 10,000-lb trailer. Ken's truck equaled the 1999 Dodge Cummins automatic we ran in October of 1999 with a 1-mile speed of 40-mph, arriving at the second mile-marker in 1-minute and 33-seconds.
Ken also owns a Duramax/Allison powered GMC truck, but chose to drive his 6.5 to the 2003 Rendezvous this time around.
The cold hard truth... Here's a shot of the marker board used to record the hill-climb performance data. Some of the later runs didn't make it onto the board, but you can still get a sense of what most trucks were capable of.
What's in store for next year? The availability of performance products for the Duramax 6600 has grown by leaps and bounds in the last twelve months. Besides having access to performance gizmos that can add up to 250 horsepower (without propane or nitrous), we're also now able to extend the limits in both vehicle top speed and governed engine rpm. Till recently, many of the high-end power products weren't of much use because of the existing Allison torque limit. Fortunately, transmission specialists like Suncoast have smashed through the factory Allison torque barrier. Uprating the Allison will have a dramatic effect on the evolution of power.
Thanks to Chris Bigley, Earnie Moran and Dr. Lee Swanger for working the hill and shooting these photos. And, thanks to all of the truck owners for showing us what their truck could do in a real-world performance test.