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February 2015 Top Diesel Tech Questions

You’ve got questions? We’ve got answers!

Jason Sands
Jan 13, 2015
Photographers: Jason Sands
Welcome to Top Tech Questions. One of our favorite forms of reader communication is tech questions. Our Top Tech section is a place where you ask what’s on your mind, and we answer. Send us an email at dieselpowertech@enthusiastnetwork.com and ask away!
How Much Can I Tow?
Question: I have a 28-foot fifth-wheel camper that weighs 7,100 pounds dry, which is almost as much as the GVWR of my ’06 GMC Sierra Crew Cab! What are your suggestions about what I should do to make towing our trailer easier on my truck and me? Thanks.
Tom Benoit
-via email
Photo 2/4   |   Modern ¾-ton (and larger) diesel trucks are designed to move large loads with ease. Unless you’re towing heavy industrial parts or a 40-foot, living-quarters trailer, the truck/trailer combination should be well under the manufacturer’s GCWR limit.
Answer: There’s some confusion about what these weight ratings actually mean, so we’re going to do our best to break it down for you. The figures manufacturers give you are (according to Wikipedia):
GAWR (Gross Axle Weight Rating): The maximum distributed weight that may be supported by the front or rear axle of a road vehicle.
GVWR (Gross Vehicle Weight Rating): The maximum operating weight of a vehicle as specified by the manufacturer, including the vehicle’s chassis, body, engine, engine fluids, fuel, accessories, driver, passenger, and cargo but excluding that of any trailers.
GCWR (Gross Combined Weight Rating): The maximum allowable combined weight of a towing road vehicle, passengers and cargo in the tow vehicle, plus the weight of the trailer and cargo in the trailer.
Even if your trailer weighs 8,000 pounds with all of your supplies loaded, and your truck (full of people) tips the scales at 8,500 pounds (16,500 total), you’re still far short of the pickup’s maximum GCWR of 22,000 pounds when factoring in both the truck and the trailer weights. Even with a ball-style bumper hitch, Duramax-powered trucks are rated to tow 12,000 pounds or more, which again is a lot heavier than the setup you’re going to tow.
But, there are ways you can overload a truck without exceeding the total GCWR. For example, we have to look back at the GAWR of the rear axle, which for an ’06 is 6,084 pounds. With about 3,000 pounds over the rear axle while the vehicle is just sitting still, adding passengers, a bed full of stuff, a fifth-wheel hitch, and the tongue weight of a trailer (which is usually about 10 to 15 percent of the total trailer weight), it is possible to push past the 6,084-pound mark, which is mostly in place as a safeguard for the rear components.
In any case, you shouldn’t be worried about towing a 7,000-pound camper—your diesel is made to move that amount of weight with relative ease. And, if you’re still worried, there’s a host of air springs, load-distributing hitches, programmers, and other aftermarket products that are specifically designed for towing that make moving heavy loads a breeze. Just remember not to exceed your truck’s weight ratings, as these products do not increase capacity.
Turbo and Injector Advice
Question: I have a Cummins- powered, ’01 Dodge Ram 2500 with the NV5600 six-speed manual, and I have put an S&B intake, MBRP 4-inch turbo-back exhaust, FASS 150-gph lift pump, and an Edge Juice with Attitude CTS monitor on it. My goals are to have a reliable, efficient, and streetable daily driver that is able to tow heavy loads but still pack a decent punch when I want it to. I plan on putting Dynomite Diesel Products 75hp injectors on it, but I was wondering if a Dieselsite Wicked Wheel would be worth the money to slightly lower my EGT and give me quicker spool-up as well as a little more midrange power. If not, could I jump up to the 100hp DDP injectors and put a BD Power Super B Single on it to maintain good fuel economy and EGT? What should I do? Thank you.
Dillon Beckner
-via email
Photo 3/4   |   Dodge Rams with the VP44 injection pump (’98½ to ’02) are quite capable trucks, despite their tendency to eat injection pumps every 150,000 to 200,000 miles. With plenty of aftermarket support, these pickups can be anything from tow rigs to 1,000hp monsters.
Answer: If you’re looking for a daily driver that packs a punch, you actually have a lot going for you. The VP44 Dodges are computer-controlled, which means they can be easily turned up for more grunt or detuned for less power (and less smoke), depending on what you’re doing. You also have a manual transmission, which gives you ultimate control over the truck and when its shift points will be. Finally, the NV5600 you have is a very strong transmission and will handle almost anything you can throw at it horsepower-wise, although it may eventually need a clutch upgrade.
So, you’ve completed your first step, and you have an intake, exhaust, and a programmer with gauges on the truck. For injectors, those made by Dynomite Diesel Performance (DDP) are notoriously clean-burning even when they’re quite large, so we’d have no problem stepping up to the 100hp injectors, regardless of which turbo you go with. Injectors have to be pretty big on VP44 trucks (200 hp or 250 hp) for the idle haze and low-rpm smoke to become too excessive.
For the turbo, we like the idea of using a Dieselsite Wicked Wheel 2, if your truck’s stock turbo is in good shape. If you’re just looking for a mild performance upgrade that will cool EGT and make some power to boot, it’s a good setup. Make sure you follow the instructions carefully when installing the compressor wheel, or have a shop perform the task, because if the wheel hits the housing due to improper installation, it’s bye-bye turbo.
If you do eventually decide to step up more in the turbocharger department, we’d go straight past the Super B turbo and buy BD’s Killer B instead. It has a smaller turbine and exhaust housing than many other turbos, and it will spool very well in your application. It has also supported up to and more than 500 rwhp, depending on how hot you’re willing to go with your EGT levels.
Finally, remember that when you’re towing with an upgraded truck, you need to keep your rpm up when pulling grades (somewhere in the 2,200- to 3,000-rpm range) to take full advantage of the increased fuel and airflow your engine will now possess.
Help, No Brakes!
Question: My question is about a soft brake pedal on my dad’s ’89 F-350 SuperCab 4x4. As far as we know, his truck is completely stock with a 7.3L, Banks Power turbocharger, and an automatic transmission. The problem is, he has replaced nearly every functional part of the brake system, except the lines (replaced some parts multiple times), yet the pedal still goes nearly to the floor before the brakes work. Was there a vacuum issue with this setup, in which not enough is produced to assist the booster? Any suggestions? It’s a great truck, but it’s not driven much because of the braking concern.
Dale Waldvogel
Peotone, Illinois
Photo 4/4   |   Often, older Fords such as this one (which was originally a gas truck) get a new lease on life by being turned into Cummins-powered hot rods or pulling trucks, thanks to their light weight and long wheelbases.
Answer: Having a soft brake pedal is actually a common problem on these older IDI- powered trucks. First, we’ll give you some tips for fixing your existing system, and then we’ll give you some pointers for upgrading the truck with an entirely new braking system.
Since you’ve already replaced most of the parts in the braking system, we’re assuming you’re not experiencing any of the usual problems, such as bad vacuum hoses or a bad booster. However, bleeding all the air out of the brake system is difficult with these older trucks. You really should bleed the brakes multiple times (at all points) to ensure there’s no air in the system.
Also, these big braking systems require a lot of pressure to move the rear shoes. So we recommend adjusting the rear brakes to a very tight setting; in other words, to a point where there is a very, very light drag on the wheels. If the rear brakes are adjusted improperly, all the pedal effort can be spent moving the shoes out to the actual stopping surface of the drums, rather than actually stopping the truck.
If the system has been adjusted and re-bled multiple times and the problem still persists, it might be time for a hydroboost conversion. A hydroboost system out of a newer truck can be retrofitted into an older one (like yours), essentially giving it the braking capability of a newer truck. Since the hydroboost system uses the power steering fluid rather than vacuum to assist braking, a new power steering pump must also be installed. There are many folks who have performed this conversion (it’s all over Google) with very good results.



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