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[HOW-TO] SLED PULL

EVERYTHING YOU NEED TO KNOW BEFORE HOOKING TO THE SLED
Truck pulling is an exhilarating sport. It’s invigorating, intoxicating, and for a lot of us it quickly becomes more than just a hobby, but rather an obsession. Due to its addictive nature, those that get into pulling rarely ever give it up, hence the reason this sport continues to grow by leaps and bounds. From brush pulls to county fairs to televised events, truck pulling is a nationwide phenomenon. It’s kind of a big deal.

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First things fi rst: Find the right receiver hitch for your needs. Whether you borrow or buy, a hitch built specifi cally for truck pulling is best. With the legal hitch height in most pulling classes being 26 inches (although some are 24 inches), having an adjustable hitch is ideal. Take this adjustable unit from Big Chevy Hitch for example. Available for both 2-inch and 2.5-inch diameter receiver openings, its receiver tube is made from cold-rolled steel, the upright is constructed of 2.5- inch hot-rolled steel bar, and it offers 12 different height positions.
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Your truck will be attached to the sled via iron hook and chain, hence the need for a roughly 3-inch diameter or larger opening in the hitch of your choice. The hook and chain extend the weight of the sled to the hitch (so a hitch tucked in as close to the truck as possible is best). In high horsepower, professionally sanctioned pulling classes, a kill switch cable will be attached prior to the chain.
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Anytime rules permit it, your truck’s rear suspension should be blocked. Eliminating rear suspension travel does two very important things: 1) It keeps your hitch height as high as possible, and 2) It limits the amount of front suspension unloading that occurs when the weight box transfers.
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Due to it being one of the more popular automatic transmissions used in sub-1,000hp pulling classes, the Allison 1000 is a perfect example of where the line can be drawn as far as what transmission gear to pull in. On higher horsepower trucks (700+), Fourth gear is most common, while Third gear is preferred for owners of lower horsepower trucks (stock turbo or Work Stock type classes). In both of the aforementioned scenarios, Lo range would be selected in the transfer case.
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Pulling with the transmission in direct drive (1:1) and the transfer case in 4-Lo is ideal. However, it isn’t always possible to achieve optimum ground speed with this combination. Furthermore, not all trucks have the power to pull off a 1:1, 4-Lo hook. Locking the transfer case in Hi range and running a lower ratio gear in the transmission has proven successful, it’s just known to be a little harder on parts.
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In trucks with automatic transmissions, locking (and unlocking) the torque converter at the right time is vital. This is why many automatic pullers opt for manual lockup switches. By being in total control of lockup, they get to dictate which gear and exactly when it happens vs. allowing the ECM to decide.
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Without a doubt, manual transmissions rule the day in the upper echelon of the truck pulling world. Due to their ruggedness, simplicity, and efficiency, they flat outperform their automatic counterparts. One of the most popular transmissions is the five-speed NV4500 (shown). With nothing more than a larger input shaft and a triple-disc clutch they can survive in applications that send in excess of 1,200 hp their way. If you’ve got a bolt-action Dodge, Chevy, or Ford, we recommend pulling in direct (1:1) and with the transfer case in 4-Lo if you can (direct is Fourth gear in the NV4500). This will create the least amount of stress for the transmission to deal with. As previously mentioned, if your horsepower level doesn’t quite allow you to run in direct, you can go down a gear in the transmission, try the Hi-side of the transfer case, or even swap out ring and pinions.
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Another solid performer in the manual transmission segment is the ZF-6 found in ’99- 10 Fords and ’01-06 GMs. While we have seen the tailhousing break on a few units, they were in high-horsepower applications (900+ hp). As with the aforementioned NV4500, pull in direct (1:1) if you can, which in the ZF-6’s case is Fifth gear, along with the Lo side of the transfer case. The same thing goes for the NV5600 six-speed found in ’01-02 HO Cummins and ’03-05 common-rail Dodges.

But what about those of us looking to enter the fray for the first time? To ease your concerns, answer any questions, and show you how to prep your truck to effectively do battle with the iron sled, we’re giving you the rundown on what it takes to put together a successful inaugural hook. We spell out everything from the type of hitch you’ll need, to the correct gear to pull in, to the suspension changes you should make, to how to leave the starting line. While lugging the sled 300 feet through the dirt is an adrenaline rush like no other, expect the first hook you make to feel more like work than fun. It will be nerve-wracking, there will be butter flies, and your mind will be racing. Your job is to embrace all of that and turn it into a successful pass by following the pre-pull game plan we’ve outlined for you this month. WARNING: Diesel World Magazine is not responsible for the impending addiction that follows…DW

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Because the turbocharger is the biggest item to police in most sled pulling classes, you’ll likely be asked to pop the hood and allow the tech official to take a look at yours before you’re allowed to hook. Stock-appearing turbo rules are easier to tech, but in higher horsepower classes (where a specific compressor wheel inducer diameter limit is required) you should be prepared to pull the air filter or air intake tube for a visual, plug, and/or caliper inspection. Such was the case in this photo, where an LMM Duramax sporting a 63mm version of an S400 was being tech’d for legality before being permitted to run in the 2.5 Class.
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Next to turbo and hitch height rules, the maximum weight allowed is of utmost importance, so expect to roll across a portable scale at the event you compete in. For diesel trucks, 8,000-pound to 8,500-pound class maximums are the norm. Any reputable pulling organization will check each vehicle’s weight prior to letting it run (and most sled owners supply a portable scale as part of the sled rental service). Some classes also offer a 50-pound grace amount should you be a tad over the maximum.
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While most entry-level pulling classes don’t allow hanging front weights, some permit you to ballast weight in order to meet the maximum weight requirement. Ballast rules typically dictate that any added weight must be safely secured, and positioned in the bed.
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If you’re signing up to compete in a class that allows hanging front weights, take advantage of it! Nothing keeps the front end digging (especially at the end of the track, where it matters most) like having extra weight forward of the front axle.
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Widening your truck’s foot print up front increases its ability to take a bigger bite out of the ground it’s covering. Opinions vary on what to air down to and different track conditions call for different pressures, but as a general rule of thumb airing down the front tires to the 20 to 30psi range is typical. Because they bear the brunt of the load from the sled (as the weight box gradually places more downward force on them), more air pressure is run in the rear tires (and a lot of pullers don’t even drop their rear air pressure).
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Tire selection itself is important as well. While it was once commonplace to solely find allterrains in classes with a DOT tire rule, mud terrains have begun to infiltrate many classes. Specifically, the Mud Grappler from Nitto Tire (shown) has become extremely popular in recent years.
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As a general rule of thumb, the longer the wheelbase the better in truck pulling. With a longer wheelbase, the front end is more isolated from the rear end as track inconsistencies are encountered during the course of a pull. Granted, regular cabs can hang more weight in higher horsepower classes, which helps, but in our experience the short wheelbase of a standard cab truck is more conducive to hopping or to the chassis becoming unsettled
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Without having the driveline and suspension reinforcement that traction bars provide, this LMM Duramax was doomed from the get-go. A hopping 7,200-pound truck combined with a foot to the floor caused this stock driveshaft to twist in two. Knowing when to let off the throttle (or stay in it) is key for any successful puller as well. At most events, you’re allowed to make a second attempt as long as you let off and get stopped within the first 100 feet.
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if you’re pulling with a Duramax, do not (and we repeat: DO NOT) crank up the torsion bars. Your front suspension and steering system is at its strongest when the CV shafts and tie rods are in parallel and everything is working in a straight line. Also, at the very least make sure you’re running tie rod sleeves to rule out a toe-in, toe-out scenario, or possible tie rod breakage.
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It’s always a good idea to power brake your truck and leave the starting line with some sort of elevated boost. Exceptions would be on desperately loose tracks where leaving the line hard will blow the tires off, or on a bumpy start. In those cases it’s best to leave soft, get through the trouble areas, and then get after it. But most competitive pullers leave with a healthy amount of boost (10-20 psi depending on the class, horsepower level, and track). After all, sled pulling is a drag race—and the first one to 300 feet usually wins.
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As for the sled you’re hooked to, the speed of the weight box, the amount of weight blocks added, and when the sled’s push-down system is set up to be triggered usually depend on the kind of horsepower the trucks in the class are making. For example, the sled will be set up completely different for a Work Stock type class vs. the mega-horsepower Super Stock trucks, which would require more weight blocks and a quicker weight box transfer speed. The sled operator’s goal for any given class is to get the trucks to stay as close to the desired 300-foot mark as possible (on a conventional 300-foot track, of course).
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While effectively being able to “read” a track is something that comes with experience, you may notice ruts, rough spots, or other trouble areas developing on the track. You can avoid them by trying a different line. To do this you have to wait until you’re the next truck to hook. After the truck in front of you leaves with the sled, simply move the traffic cone (it will be positioned at the rear, center of the sled when it’s stopped on the starting line) to your preferred side of the track. The sled operator will know to position the sled according to where this cone is.

PICK THE RIGHT GEAR(S)

One of the most important formulas to know in the sled pulling game is final drive ratio (multiply transmission gear ratio x transfer case gear ratio x ring and pinion ratio). Most 2.5 Class and hot-running street trucks will fall into the 11 to 13:1 range, but they’re typically packing 850 rwhp or more. The easiest way to make sure you pull with an optimized final drive ratio is to lock the transfer case in 4-Lo and find out which transmission gear allows a ground speed between 25-30 mph to be achieved. If you can’t find what you’re looking for in 4-Lo, try the Hi-side of the transfer case and select a lower gear in the transmission. Take a look at the chart below to see what a lot of 700 to 900rwhp trucks run. Keep in mind, however, that with varying horsepower levels, transmissions, 4-Lo vs. 4-Hi, and different axle ratios taken into account, each individual truck’s setup will be slightly different.

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This is a feature we wish every sled came with: a digital readout for distance traveled. Ground speed would be nice to know, too… Trust us, visually seeing the distance traveled rather than having to decipher exactly what the announcer is saying over a muffled PA system is a welcomed luxury. And knowing how fast the trucks actually run would be eye-opening for a lot of spectators.
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Truck pulls almost always draw a considerable crowd. Even at local county fairs, hundreds often turn out to watch the dirt fly—so expect plenty of onlookers to watch you lug the sled down the track. No pressure!

 

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