Once a fledgling class full of hot street trucks, the 2.6 Class has turned into one of the most popular sled pulling categories in the nation. With vehicles only requiring a stock-style driveline, a 2.6-inch-inducer turbocharger, and not much else, a lot is left open to strategy. To get the lowdown on what makes one of these rigs tick, we sat down with Haisley Machine employee Rob Wright, who won the Saturday night pull at the 2015 Scheid Diesel Extravaganza. Rob also won in 2013 and 2014, which makes it three years in a row for him and his ’95 Dodge Ram 2500.
| 002 Rob 26 Puller Engine Bay
When you pop the hood on Rob Wright’s ’95 Dodge Ram 2500 sled puller, one of the first things you might notice is its lack of a cooling system. Since both the engine block and cylinder head are filled with Hard Blok, a radiator and water pump are not needed.
| 003 Rob 26 Puller 1300hp Engine
Class-specific engines for sled pullers are some of the most advanced diesels on the planet. With 1,300 hp out of a 6.4L Cummins engine and a single turbocharger, Rob Wright's powerplant makes 3.3 hp per cubic inch!
| 004 Rob 26 Puller Dampener
A strong bottom end is vital for a pulling engine’s longevity over the course of a full season. The 6.4L is founded on a sleeved and deckplated 6.7L block, with an internally balanced crankshaft, a set of “custom” rods, Ross Racing pistons, and a custom flat-tappet camshaft. An SFI-rated Fluidampr balancer keeps harmonics in check when the engine is turning 4,000 to 4,500 rpm.
| 005 Rob 26 Puller Front Cover
The mixture of mechanical and common-rail fueling parts requires some custom pieces. A big part of making everything work is the front cover, which adapts the P-Series injection system to the newer 6.7L block.
Reaching New Performance Heights with a 6.4L Cummins
Perhaps the first question Rob (or anyone else in the 2.6 Class) gets asked is: “How much power does the engine make?” After all, it’s limited to using a single 2.6-inch-inducer turbocharger (66 mm), which is usually good for about 900 to 1,000 hp. So when Rob told us the 6.4L Cummins in his truck puts out 1,300 hp at 4,500 rpm, the first thing we wondered is where that extra 300 hp comes from.
“In 2011, we were at about 1,000 hp on an engine dyno,” Rob says. “Since then, we've seen improvements in head flow and intercooling, turbocharging, and injection systems, which have allowed us to extend power well past the levels we initially thought were possible.” A lot of magic lies in the Jeb Modern Machines Holset HX60-based turbo, which has been fitted with a custom compressor wheel and housing. “A lot of people are surprised to learn that we only run about 45 to 50 psi of boost, but it's a very efficient setup,” Rob adds.
In addition to the power gain, there has also been a huge improvement in the engine’s reliability in the past few years. Rob runs a Haisley Machine “Super B” Cummins long-block, which is essentially a 6.7L block that's been sleeved and filled and has a steel plate incorporated across the top of the deck. This treatment is known as “deck plating,” and it allows Rob to run tunes that are right on the ragged edge without worrying about cracking a block. “We used to go through a number of engines in a season. If you weren't pushing things to the limit, somebody else would be, so everyone just ran as hard as they could—which resulted in a lot of failures,” Rob says. Now with the Super B, completing an entire season of sled pulling is no problem at all.
| 006 Rob 26 Puller Lift Pump
The fuel system is one area that is extremely overbuilt, as a pressure drop (to the high-dollar injection pump) can spell disaster for the engine. The Waterman Racing Components pump is driven by the crankshaft, supplies up to 100 psi, and can flow a crazy 600 gallons per hour.
| 007 Rob 26 Puller Northeast 13mm Pump
Although it’s P-Series based, the 13mm Northeast Diesel Service injection pump is highly modified. It allows full fueling up to 5,000 rpm and is set at 650 cc per 1,000 strokes of fuel, although it’s capable of flowing much more.
| 008 Rob 26 Puller Top Feed Injectors
Rob is pretty tight-lipped about the specs of the wild MJ Tool and Fab top-feed injectors, but he hints that they flow somewhere in the range of 800 percent more than stock.
| 009 Rob 26 Puller HX60 Based Turbo
A long time on an engine dyno was spent getting the turbocharger just right. The Holset HX60-based turbo features a custom compressor wheel that’s clipped down to 2.6-inch (66mm) specs, along with a unique race cover. Rob estimates the custom unit is worth about 200 to 300 more horsepower than an out-of-the-box turbo!
Putting the Power on the Pavement
If you think that putting 1,300 hp and 2,000 lb-ft of torque through a factory drivetrain is murderous on parts, you’re right. On Rob’s truck, the brunt of the load is taken by a Dana 80 rear axle, which has been fitted with a spool, Branik Motorsports 37-spline axles, and a rear differential cover that incorporates carrier bearing supports. “Still, we broke eight rear ring and pinions in 2015, and three more up front,” Rob points out. “We tried everything. We cryogenically treated them; we went the other way and heat-treated them. Nothing we used was able to keep the rearends together for any significant amount of time.”
Despite the rear-axle crisis, we’re impressed by the number of parts that retain their factory lineage. The transmission, for instance, is a stock NV4500 five-speed manual that has only been upgraded with a billet input shaft and a Haisley Machine triple-disc clutch. The transfer case is factory, too, although it has been welded and locked into 4-Low, since that's the only range Rob uses. The driveshafts are nothing fancy, either, with the exception of their tough 1480-series U-joints.
| 010 Rob 26 Puller Air To Water Intercooler
The more weight at the front of the truck, the better. So a huge, Chiseled Performance four-core air-to-water intercooler is mounted where the radiator used to sit. The ’cooler chills 500-plus-degree compressor air to slightly above ambient temperature.
| 011 Rob 26 Puller ATS Manifold And 14mm Studs
Some parts on Rob's engine are quite exotic. The head studs are 14mm instead of 12mm and are made from ARP's 625 Custom Age material. The 24-valve head is also ported and polished, and its fitted with oversize valves, Smith Brothers pushrods, titanium valvesprings, and billet rocker bridges. Oddly enough, the rocker arms are stock, and Rob says he's never had a problem with them.
| 012 Rob 26 Puller NV4500 Transmission
Perhaps one of the least trick parts on Rob's Dodge Ram is the NV4500 five-speed manual transmission, which is just as the factory built it—with the exception of an oversize Haisley Machine input shaft and triple-disc clutch. Rob launches in Fourth Gear and never shifts during an entire pull.
| 013 Rob 26 Puller Transfer Case
Rob modified the 241DHD transfer case to remain locked in 4-Low.
Experience Is Key
“Gaining experience is critical for having success in sled pulling,” Rob explains. “Not only does the number of years you've been pulling matter, the things you try during a season are also very important. I’ve traveled to different tracks, hooked up to many different sleds, and I'm constantly trying new things. I've probably tried five or six different hitch setups alone.” Rob is also vigilant when it comes to “reviewing tape.” His wife videotapes nearly all his pulls, and after every event, Rob goes back and reviews each hook to see how it went, what he did, and what he could have done differently. “I try to watch as many pulls as possible before, during, and after an event to analyze the stuff you don't see when you're in the heat of the moment,” he says.
| 014 Rob 26 Puller Gauges
The dash in the ’95 Dodge Ram 2500 isn't full of gauges or a sophisticated data logger. “We spend so much time on the dyno, we already know just about everything the engine does during a pull,” Rob explains.
Taking Luck Out of the Equation
“After all the effort we put into doing this, anybody can have a bad run or an unbelievable night based mostly on luck,” Rob laughs. “I've seen track conditions go from good to bad, then back to good, then bad again—all in one night. I won the Lucas Oil Pro Pulling League event at Rudy's Diesel Performance Fall Truck Jam in 2015, but most of that was due to the luck of the draw and the good fortune I had of pulling while the track was on a good streak. That's why most of us compete in a points series. After building a top-of-the-line truck and learning how to drive it, there's still both luck and strategy involved in winning. With enough pulls, a lot of the luck is taken out of it.”
| 015 Rob 26 Puller Front Double Coil Over Suspension
Rob isn't afraid to try new things to keep his truck at the top of the pack. The front suspension is a unique double-coilover setup, with a normal coilover shock inside of a factory-style coil spring. The theory behind this setup is that it's extremely variable in its damping rates, which helps the truck hook as it shifts its weight from front to back multiple times while headed down track.
The Future of the 2.6 Class
“We just couldn't continue with the parts breakage the way it was,” Rob says. “So, a lot of pullers got together and made a vote. In 2016, an ‘open driveline (no front or rear axle requirements or restrictions)’ will be allowed in most points series’ 2.6 Class.”
With the change to an open driveline, look for the 2.6 Class to be more competitive than ever, as breakage becomes less of a factor. In the next few years, we wouldn't be surprised to see power levels climb even further as well, to as high as 1,400 and 1,500 hp. One thing's for sure, though: As technology progresses, so will Rob and hisl’95 Dodge Ram 2500.
| 016 Rob 26 Puller Front Nitto Mud Grapplers
“The person who gets to the 100-foot mark with the most speed usually has a good chance of winning,” Rob says. To help the front end hook out of the hole, Rob runs aggressive 35x12.50R17 Nitto Mud Grapplers, which are mounted on 17x10 Real Racing Wheels.
Behind the Wheel
“The engine has a lot of airflow, so I try not to rev it up past 4,500 rpm on the starting line. I use a hand throttle instead of a foot throttle for better throttle modulation and to avoid “jumping up and down on the pedal” on a rough track. When it feels about right, I start letting out the clutch and rolling into the throttle at the same time to keep the engine in the 4,000- to 4,500-rpm range. Everything happens rather quickly, because by 40 feet, I’m usually at full throttle, and a few feet later, I’m off the clutch entirely. As I go down track, I’m looking at the tach, the hood stack for potential issues, and the flagger for the red “stop” flag. If the truck starts to drift out of line a bit, I'm careful not to overcorrect, as too much steering slows you down more often than it helps. When the truck's digging in at the end, horsepower and chassis setup are doing most of the work. I just keep the hammer down. Once I see the red flag, I chop the throttle, then look around to see how I've done. It's amazing how much work you put into driving a truck in just 300 feet."
| 017 Rob 26 Puller Dana 80 And Driveshaft Loop
A reinforced Dana 80 rearend with a Liberty's High Performance Products custom spool and 37-spline Branik Motorsports axles resides in the rear of the truck. The Dana 60 up front has a Yukon Gear and Axle Grizzly locker and 37-spline Branik Motorsports inner axles. The driveshaft loops are there in event of driveline or rearend breakage occurring, which seems to be frequently.
Recent Major Event Wins and Series Accomplishments:
Lucas Oil Pro Pulling League (PPL) Champion, 2014
Scheid Diesel Extravaganza (SDX) Friday night, First Place, 2014
Lucas Oil Pro Pulling League (PPL) Second Place, 2015
Ohio State Tractor Pullers Association (OSTPA) Second Place, 2015
Scheid Diesel Extravaganza (SDX) Saturday night, First Place, 2015
Rudy's Diesel Fall Truck Jam 2.6 Class First Place, 2015
| 018 Rob 26 Puller Rear Dual General Grabber AT
Virtually all sled pullers in the 2.6 Class (and up) run dual rear wheels when the rules allow it. For traction at the rear of his truck, Rob relies on four 35x12.50R17 General Grabber All-Terrain tires on 17x10 Real Racing Wheels.
The Cost of Running a Puller
“If nothing breaks, there are still quite a few maintenance items we need to address,” Rob says. “The oil is changed every six to eight passes, and the cylinder head studs are re-torqued. We also check the valve lash. The tires last two to three seasons, but I usually adjust the clutch every three to four weeks, as I like a certain feel. The engine used to be an issue, but its now very reliable, just as the driveline will be once we go to an open driveline.”
| 019 Rob 26 Puller Hitch
Hitches are usually one part of the equation that pullers are pretty quiet about, and Rob is no exception. Rob says Jason O'Brien at Performance Truck and Tractor has been a big help with chassis advice.
“There's a lot of safety equipment for both myself and the truck,” Rob says. “We have transmission blankets, clutch shields, fire jackets, shoes, helmets, and neck braces. In 2013, I had a camshaft break, and I got rear-ended by a 40,000-pound sled at about 30 mph. Neck braces were optional at the time, but one concussion later, and I definitely wear one now! Whether you think you need it or not, all the safety equipment is there for a reason and isn't something to skimp on.”