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Diesel Tech Questions: You Have Questions-We Have Answers

Top Tech

Bruce W. Smith
Jul 23, 2018
Photographers: Bruce W. Smith

Tall Towing Order

QUESTION: I ordered an ’18 Ford F-350 with a 6.7L Power Stroke diesel engine. It’s a huge step up from the road-weary ’03 Super Duty (with the 7.3L powerplant) it’s replacing. The new truck will be used to tow one of two 20-foot Big Tex equipment trailers, or a 40-foot XLR Nitro gooseneck toy hauler. All three trailers weigh between 15,000 and 17,000 when loaded. I plan to put a 6-inch lift and 37-inch tires under my new truck. What is the best suspension setup for this type of use?
Jeremy Stiles
via email
Photo 2/7   |   Big lift kits look awesome and definitely set some trucks apart from others. However, the downside for towing with a lifted rig is the modification also changes its handling dynamics, requiring multiple changes in trailer and hitch setups. It pays to research those issues prior to investing in big suspension/tire/wheel upgrades.
ANSWER: The difference 15 years makes in diesel pickup technology related to towing capacity, handling, comfort, and safety is mind-boggling. The ’18 Super Duty is proof of this for sure. If your new truck is ordered with 3.55 gears, Ford’s maximum tow rating for both conventional towing using the factory bumper hitch and towing with a weight-distributing hitch is 15,000 pounds according to the 2018 RV& Trailer Towing Guide found at fleet.ford.com. The maximum gooseneck capacity for the same pickup is 20,000 pounds. So the new rig is perfectly capable of safely towing your fifth-wheel setup as it comes equipped from the dealer, along with the equipment trailers—as long as the latter are kept under 15,000 pounds loaded trailer weight. Tow heavier and you risk serious liability concerns for both yourself and your company in the event an accident occurs while towing more than the maximum stated in the vehicle manufacturer’s towing guide. Which brings us to this: Lifting a vehicle reduces (or negates) the tow ratings. When you modify the stock suspension and/or tires and wheels, despite how awesome it looks, there are hidden drawbacks related to towing. The higher stance and taller tires raise the center of gravity while reducing braking and engine performance because of the change in effective overall gearing and addition of unsprung weight. Of more concern from a safety perspective are the ill effects a lift imposes on the truck because of the trailer. An aftermarket suspension reacts differently than the stock setup. So ask the suspension manufacturer some very direct questions related to how its lift kit affects your truck’s tow ratings and overall handling. Also, consider installing helper air springs with a lift to help stabilize the rear suspension, along with upgrading to heavier front and rear sway bars (if any are available) to offset the higher center of gravity. Then, you’ll need to find a “Class V” adjustable drop-shank hitch capable of handling the weight of the two equipment trailers. (Note: Using a reducer to take the Ford 3-inch receiver down to 2.5 inches also reduces the pickup’s maximum tow rating). Keep in mind the tongue weight (TW) on trailers towed on the ball or pintle hitch need to be between 10 and 15 percent of the loaded trailer weight for optimum handling. We recommend checking out Curt, Reese, B&W, and Gen-Y Hitch offerings for your proposed application. You also need to make sure your fifth-wheel’s neck can be shortened enough to clear the bed when a lift is installed. In some situations, it can’t, so a lifted truck may also require dong an “over-under” spring conversion on the trailer to get the tandem to match up properly.

Coding Ford 6.7L

QUESTION: I have a ’16 Ford F-350 with 43,000 babied miles. The truck is maintained by the book, with oil and all filters changed well before owner’s manual says to. While towing a 13,000-pound fifth-wheel trailer during a long vacation, the truck suddenly lost power and a “Reduced Engine Power” message flashed on the screen. My handheld scanner recorded two diagnostic-trouble codes: P0087 and P0170. It’s being transported to a local Ford dealer to get whatever repairs are necessary—hopefully all under warranty. I run Stanadyne fuel treatment in every tank of fuel and try to only fuel up at the big truck stops or Shell and Chevron stations.
Marty Diel
via email
ANSWER: We checked with Tripp Trucks, a highly respected Ford diesel repair center in South Carolina, and asked about the diagnostic-trouble codes and “limp home” issue. They say some ’15 and ’16 Super Dutys experience code P0170 (Fuel Trim Bank 1) coming on randomly and popping up again even after it has been cleared. Tripp technicians follow Ford’s TSB 16-0134 in those instances, reprogramming the ECM with the latest calibration, which also removes the DTC. The P0087 (Fuel Rail Pressure Too Low) code indicates there is a fuel-delivery concern, typically set off by clogged filters, a bad high-pressure pump or injector, rust or other contamination in the fuel system, and so forth. The first corrective action is replacing the fuel filters and making sure the water-separation filter is drained. “It just takes one bad batch of fuel to clog filters and create havoc in the 6.7L fuel system,” says Kenneth Tripp, a former member of Ford’s diesel development team and owner of Tripp Trucks. That’s why it’s always good to have at least one set of spare fuel filters when traveling outside your local area, because you don’t know the quality of the fuel. If it’s not an issue with the fuel filters and the fuel tank shows no sign of internal rust or contamination, the dealer will probably perform tests to ensure the injectors are OK, as well as the fuel-pressure control valve, which is also known to fail. As a last resort, many Ford dealers replace (under warranty) the entire fuel system, from pump to injectors, using a Motorcraft Fuel System Contamination Repair Kit (PN EC3Z9B246A). The kit contains all the parts that make up an ’11-to-’16 6.7L fuel system under one part number.

RAM G56 Lube

QUESTION: The stock clutch in my ’16 Ram 3500 is shot. I’m replacing it with a South Bend twin-disc because I transport RV trailers from California to Florida. The original clutch didn’t last as long as I hoped it would (62,000 miles). While the transmission is out, I’m having the fluid replaced, which the owner’s-manual maintenance schedule calls for at 60,000 miles. South Bend Clutch recommends using premium 50W synthetic gear oil instead of the automatic transmission fluid Ram recommends for the G56 six-speed manual transmission—and adding a quart more than the factory specifications. Why the heavier gear oil with an extra quart?
Jack Brown
via email
Photo 3/7   |   A growing number of diesel-powered-Ram owners are refilling their trucks’ G56 six-speed manual transmissions with either 75W-90 gear oil or SAE 50 synthetic engine oil instead of using the recommended automatic-transmission fluid. They also add an extra quart (or two) to lessen harmonics from the engine and clutch, and to smooth shifting.
ANSWER: The extra quart of oil in a G56 six-speed manual transmission is said to lessen the harmonics (noise) transmitted from the engine and twin-disc clutch assembly, and the thicker oil helps improve shift quality, according to Manseil Washburn, head of South Bend’s diesel-clutch department. The Mercedes-Benz transmission is built in Europe and many North American Ram owners have departed from the ATF and adopted the higher-viscosity 75W-90 gear oil or SAE 50 synthetic engine oil, which is recommended for European trucks using the same transmissions. The downside to consider when replacing ATF with SAE 50 or 75W-90 is the fact that those oils have significantly heavier viscosity than ATF. Remember, gear oils use a different viscosity scale than engine oils, so SAE 50 engine lubricant is actually thicker than 75W-90 gear oil. So, a G56 is going to shift smoother and easier in 45-degree (Fahrenheit) or colder temperature when filled with the recommended ATF than loaded with a premium synthetic SAE 50 or 75W-90. ATF also runs cooler than those higher-viscosity lubricants, which can be of great concern for those trucks with power modifications or that do a lot of heavy towing and hauling in hotter climates. Heat, by the way, is the G56 transmission’s biggest enemy, because it causes the case to expand; transmission experts say when oil temperatures are consistently above 220 degrees, shaft clearances and bearing tolerances can fall out of specification and result in transmission failure. As for refilling your six-speed manual, Ram calls for 4.95 quarts of ATF+4 in a G56. Some shops we spoke with say they replace the ATF with 6 quarts of SAE 50 lubricant. We know of others that put in 2 extra quarts of fluid, whether 75W-90 or SAE 50. We don’t recommend that much overfilling, because more oil in the case just means there is greater heat retention and buildup.

LBZ Allison

QUESTION: How much extra power can a stock Allison automatic transmission behind a 6.6L Duramax LBZ engine handle? I just had my ’06 Chevrolet Silverado 2500HD set up with a Stage 1 Garrett turbocharger, along with a cold-air intake, 4-inch exhaust, and a 100hp EFILive ECM calibration. I tow a 26-foot toy hauler quite often and use my truck to commute to work. I’m not into the hot-rodding, I just like keeping up with traffic when towing. The truck runs really strong now, but one of the mechanics at the shop where I had the work done suggested I get the Allison upgraded. Should I trust his advice?
Brady Wills
via email
Photo 4/7   |   Be aware that stock Allison six-speed automatic transmissions are perfectly capable of providing many trouble-free years of service under normal conditions. But, without internally modifying the gearbox, increasing a Duramax engine’s power output by more than 50 hp could reduce that longevity considerably—especially when the transmission is subjected to towing heavier trailers.
ANSWER: Questions such as this are always up for debate. But, yes, from the Allison experts we’ve spoken with, you need a stouter transmission. The six-speed should be OK handling mild tunes that bump the Duramax engine’s horsepower by 40 to 50 hp. Anything more than that—especially when subjected to the extra stress placed on the drivetrain while towing—is asking for trouble and a short-lived transmission. As you have seen and felt, the new turbo and modifications already helped improve the engine’s power. But a heavy right foot coupled with a 100hp tune is a sure path to spending more time and money in the transmission shop. One temporary solution to support that calibration is to have the stock transmission upgraded with a shift kit until you can invest in an Allison that’s upgraded with the internal parts required to handle the higher horsepower and torque necessary for towing and racing applications.

Battery Life

QUESTION: How do I know if I should replace the second set of batteries on my ’06 Ford F-250? They’re almost five years old, and it seems most diesel-truck batteries die when they are between four and five years old. I just don’t want these to die on me in the winter when I’m forging my way across the snowy plains here in the upper Midwest.
Steve Zimmerman
via email
Photo 5/7   |   Battery longevity is dependent on many factors, including the type of batteries in your diesel truck and how they are used and maintained. High-end, high-CCA deep-cycle batteries typically last more than five years if treated well. Have the cells load-tested once a year starting at their warranted “half-life,” as a way of keeping tabs on their health.
ANSWER: Battery life is dependent on many factors, ranging from the type of battery to the way it’s maintained, climate it’s used in, and how it’s being used. A well-maintained set of high-quality, deep-cycle, high–cold-cranking-amp (CCA) absorbed-glass-mat (AGM), and gel-cell batteries, like those offered by Optima and others, typically last five years or more in normal use situations. If the batteries are poorly maintained or drained down a lot during winching, powering a lot of accessories, or used in very hot or cold climates, their life can be greatly shortened. That’s why it’s always good to start checking their condition around their rated “half-life,” because an underperforming set of batteries can cause many issues with today’s diesel fuel injection systems, sometimes taking out fuel injection modules and triggering diagnostic-trouble codes. As we all know, cold weather is where batteries get their biggest test, so any weakness will rear up when the temperature drops below freezing and the key is turned to crank over a cold diesel. Our suggestion: Drop by one of the chain auto parts stores and have the batteries load-tested (major retailers usually do this for free), and then get a second opinion. Better still, buy an inexpensive, 500-amp carbon-pile load tester and check your truck’s batteries at home. Read and follow the instructions regardless of the brand load tester you use! If you are trying to get every last cent’s worth from the batteries in question, just run them until one dies, then replace both. Always replace dual batteries in matched pairs, or the weaker battery will shorten the life of its mate. It’s also prudent the replacement batteries have at least the CCA of the original batteries—and new batteries with a higher CCA are even better. While replacing them, take a few extra minutes to clean the battery cable ends, look for any signs of corrosion where the battery cables attach to the terminal ends, and make sure the grounds are clean and tight. After the new batteries are hooked up, coat the battery connections with a protective coating, such as CRC’s or Permatex’s battery terminal protector/sealer, to slow down corrosion.
Photo 6/7   |   Top Tech Diesel Battery

Manual Regen

QUESTION: I have a ’16 Chevrolet Silverado with a 6.6L Duramax LML engine and do a lot of local, city, non-highway driving for work, which also includes more than average idling time. Is there a way to manually get the diesel particulate filter to regenerate without taking the truck to a dealership service department or wasting the time finding a place to drive 55 mph for 30 minutes? I would like to do the regen while truck is parked.
Andy Leach
va email
ANSWER: Some programmers include a manual-regeneration setting. For example, if you use an Edge Products Insight or Evolution CTS 2, select the “diagnostics” mode, then scroll to the REGEN screen. Read and answer all the “Yes” or “No” questions that appear on the monitor and read the safety instructions and warnings closely: First, park the truck in a location away from anything flammable. Regens create a ton of heat at the exhaust pipe, so being outdoors on gravel, asphalt, or concrete is a must. With the transmission in Park, open the hood and begin manual regeneration. When the regen cycle starts, the engine could be turning 2,500 rpm until the DPF is cleaned out and the regen cycle is completed. Regen cycle times (20 to 40 minutes) depend on the amount of clogging inside the DPF. If you are using an older CTS 2, download the most current update, which should allow manual regens for both GM and Ford. If you have a different brand programmer, dig out that owner’s manual and see if it has a similar function.

Rattling Clutch

QUESTION: I had a South Bend Clutch SDD3250 twin-disc clutch put in my warmed-up ’12 Ram 2500. Three months later, it started making a lot more noise than it did when first installed. I’m worried. Is the clutch going bad already?
Brandy Hastings
via email
Photo 7/7   |   Twin-disc clutches have a “floater” plate that fits into the clutch assembly. South Bend Clutch’s “center plate” uses special polyurethane snubbers on each of its four alignment ears to reduce noise and vibration. When the snubbers wear out or come apart, the clutch makes a lot of racket when the pedal is depressed.
ANSWER: All twin-disc clutches make noise. It’s typically caused by a floating pressure plate residing between two clutch discs, which vibrates when the clutch is pushed in. What might be happening is the two fingernail-sized polyurethane snubbers on each of the plate’s four alignment ears may be deteriorating, causing the plate to rattle. If that’s the case, at some point, depending on how loud the rattling noise gets and your tolerance level, the clutch will need to be removed and those snubbers replaced. Manseil Washburn, head of South Bend’s diesel-clutch department, says “Those [snubbers] would have to come directly from us, and we normally don't charge for them.” He adds that hard jolts on the clutch assembly (that occur when spinning tires contact firmer ground, under fast shifting, or heat generated from slipping the clutch too much) contribute to snubbers failing (or coming out), which is common when backing trailers. When the snubbers are replaced (they easily tap in with a small ball-peen hammer), also change the throw-out bearing. Driven properly, a twin-disc clutch should last more than twice as long as a single-disc.

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