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Diesel Tech Questions: You Have Questions- We Have Answers

Top Tech

Bruce W. Smith
Aug 20, 2018


QUESTION: I own a ’14 GMC Sierra 3500 Denali and 33-foot fifth-wheel trailer. The loaded RV should weigh around 13,500 pounds when my wife and I hit the road, and our truck has 127,000 miles on it. After following your magazine for the last two years, I’ve decided to address a few Duramax-related items, with hope that the upgrades will make my truck’s engine more reliable. I’m going to install a performance intake, along with an aftermarket lift pump and freer-flowing exhaust. My goals are reliability and improving fuel economy. What ECM calibration will be the best one for pulling this all together? I’ve read a lot of forums that say EFILive is great.
Will Wilson
via email
Photo 2/5   |   A “tow tune” that increases the 6.6L Duramax LML engine’s torque and horsepower about 10 percent over stock is a good choice when trailer towing is a truck’s primary use. Just keep in mind a stock Allison six-speed automatic transmission doesn’t have a high tolerance for big horsepower or torque gains. Another upgrade to consider for a used Duramax LML engine is a CP3 injection pump conversion.
ANSWER: When pulling a big trailer full time with a 6.6L Duramax LML-powered rig, there are a couple of changes for reliability and comfort we recommend. While a freer-flowing air intake is always helpful, the overall mpg gain from adding the cold-air intake, lift pump, and exhaust won’t be much better than stock when the truck is towing nearly 7 tons of trailer. We figure the improvement is about 10 percent at best. Leave the muffler in place, because the drone from a straight exhaust can be very bothersome when towing—especially over long distances—as can the smell of diesel exhaust leaking into the cab. For ECM tuning, a stock or mild “tow” calibration from EFILive is a good choice. The calibration will increase torque and horsepower about 10 percent over stock. Just keep in mind the fact that the stock Allison automatic transmission doesn’t have a high tolerance for big horsepower/torque gains, so it can become a weak point in the drivetrain. One upgrade we suggest you definitely consider is doing a CP3 injection pump conversion: The Duramax LML engine’s CP4 injection pump’s failure rate is a concern that is widely discussed on many diesel-enthusiast online forums. When a CP4 fails, repairing all the damage it causes costs more than having the conversion done. The CP3 is, for the most part, bulletproof. For maximum reliability, keep a very close eye on EGT and use a light right foot when you’re pulling the fifth-wheel trailer. Tow with the transmission in Fourth or Fifth gear, and always use tow/haul mode. Don’t lug the engine while towing. Take your time and enjoy the scenery.


QUESTION: I installed a new South Bend clutch, resurfaced the flywheel, and installed an all-new pilot bearing, clutch fork, pivot ball, and release bearing on my ’01 Dodge Ram 2500. The resurfacing was done by a local and reputable transmission supply house, which is also where I bought the parts. The new pilot (needle bearing) froze after 30,000 miles and would keep spinning the transmission, so I had to shift without using the clutch. The transmission shop says the problem is common for high-mileage NV5600 transmissions (my truck just passed 270,000 miles), so they suggested milling the flywheel and pressing in a sealed bearing with a brass inner sleeve. I was wondering what Clutch Masters would recommend, as this part (pilot bearing wear) is not mentioned in the “Clamping Force” (Diesel Power, June 2018) article.
Casey Haveman
via email
ANSWER: The advice from your transmission shop is spot-on, Casey, and exactly what South Bend actually recommends to customers when doing a clutch replacement on higher-mileage diesel pickups. “With that many miles on the transmission, the input shaft wears, causing the stock bearing to go bad prematurely,” says South Bend’s Manseil Washburn. “The correct fix is to replace the input shaft in the transmission, bore out the flywheel, and install our heavy-duty sealed roller bearing.” As for the clutch used in the “Clamping Force” article you referenced, Clutch Masters says it was one of the very first flywheels offered by the company, and it, indeed, had a roller pilot bearing. However, since the release of those early production units, the plate now has a sealed pilot bearing. ”We have definitely listened to the market’s concern about this very issue, and we have gone away from using them on all current products,” says Clutch Masters’ Travis Booher. Clutch and transmission rebuild expert Gary Haslip, owner of Geezers Garage in Coburg, Oregon, says concerns about the longevity of needle-type pilot bearings in high-mileage diesel trucks with manual transmissions are justified because of movement caused by excessive crankshaft end play and/or from the transmission’s input shaft. Gary says when replacing the clutch on any high-mileage, manually shifted vehicle, it’s prudent to check crankshaft end play, input shaft play and wear, and flywheel run-out, and compare those numbers to the stock specifications and tolerances. Such thrust forces will cause excessive heat in needle-type bearings, which are designed to handle only radial forces. Sealed roller-style pilot bearings are designed to handle both radial and thrust loads. The new pilot bearing will also be riding on the fresh surface of the input shaft, and you may find the transmission shifts smoother because of the pilot bearing swap.


QUESTION: I am giving a ’49 Ford F3 (1-ton) a new life. Instead of going “old school” and dropping in a 4.6L or 5.0L Coyote V-8 engine, I want to slide a Cummins R2.8 diesel into the old workhorse. Where can I find the adapter to mate the Cummins to a 4R100 automatic transmission from a ’99 F-250? My plan is to rebuild the 4R100 the same way you guys did in “Rock-Solid Automatic: The Makings of a Bulletproof Ford 4R100 Transmission” back in 2010 and get a custom radiator/intercooler built so the old F3 looks stock until you open the hood.
Zeke Winston
via email
ANSWER: Sounds like you’re taking big step up in technology and performance. The F3 was originally equipped with a 101hp, 215ci I-6 or optional 100hp, 239ci V-8. The 161hp Cummins R2.8 has found tremendous popularity in the diesel “repower” market, and it’s ideal for use in restorations. The R2.8 is almost the same physical size of the Ford 302 Windsor, 5.0L Coyote, and 4.6L SOHC V-8s, measuring 25 inches long by 25 inches wide by 28 inches high. So if a V-8 can be dropped into old iron, the R2.8 diesel can, too. The baby Cummins is a crate engine, with its wiring harness and computer all in one plug-and-run package. The other good news is popularity has sparked numerous adapters and kits to slip Cummins’ I-4 diesel into a wide range of light-duty applications and transmission combinations. We talked to Kevin Silovich at Axis Industries (axisindustriesusa.com)—a major player in custom adapters and kits for R2.8 conversions—about mating the crate engine to the Ford 4R100. Here’s the inside scoop: Kevin says “at the present time,” it’s a no-go on older Ford automatics; no one has made the adapters because there’s not yet enough demand. Right now, the ideal combination for what you are doing is mate the Tier I R2.8 to either a GM 6L80E automatic, or drop in a ZF 8HP70 similar to the automatic gearbox in 3.0L EcoDiesel Rams, Jeep Grand Cherokees, Range Rovers, and a plethora of other Chrysler products. The adapter kits are on the shelf and ready to go. Kevin says the newer electronic six- and eight-speed transmissions are the most compatible units to the R2.8’s electronics, providing the best overall streetability. Basically, either one is close to being plug-and-play with a standalone wiring harnesses. “Low-mileage versions of both automatics can be found for as little as $1,000 from auto recyclers,” Kevin says. And, by the time this article is published, Axis hopes to have the complete R2.8 conversion kits, including transmissions, in its growing inventory. We also know Zero Gravity Performance (zerogravityperformance.com) has GM standalone conversion kits for less than $4,000 that include the GM 6L80E transmission, torque converter, wiring harness, and so forth. The other concern you need to address is making sure the F3’s final-drive ratio (axle ratio, overdrive ratio of the automatic, and tire diameter) falls within the engine’s optimum operating rpm curve. The reason the new multiple-overdrive, six- and eight-speed automatics are such a good match with the little diesel is because they have a wide enough spread of ratios to make the engine perform well.


QUESTION: I have a ’96 Dodge Ram pickup with a 5.9L Cummins engine and automatic transmission. The truck has a Banks Power PowerPack kit along with a BD Diesel Performance charge-air cooler and a fabricated 3-inch air horn. The truck has 160,000 miles. My problem is excessive EGT when towing. Temperature easily and quickly reaches 1,400 degrees while driving in the 1,500- to 2,000-rpm range, with 8 to 15 psi of boost. I have tried using Snow Performance water-methanol injection, but on longer pulls, the mixture completely kills one cylinder, even with a small nozzle. I replaced the injectors with Bosch 50hp pieces, but doing that didn't help lower EGT. I reinstalled the stock fuel plate and that slowed the increase, but the temperature is still getting too high. The exhaust doesn’t spew black smoke, only a slight haze when the engine is pulling hard. It makes great power, but I just can't use it. None of my friends with newer, higher-horsepower diesels have exhaust pyrometers, so I have nothing to compare mine with. What EGT should I expect under a moderate load?
John Gaede
via email
Photo 3/5   |   Top Tech Hot Towing
ANSWER: Typically, we consider 1,200 degrees to be a “safe” towing EGT. As we noted in a previous tech column, exceeding 1,300 degrees “pre-turbocharger” for an extended period of time, such as pulling a long grade with a heavy trailer, is asking for a good day to turn bad. That’s why we always recommend any diesel owner have a good way to measure EGT, whether through a programmer or standalone pyrometer/gauge setup. Older Dodge Rams with automatic transmissions are unique when it comes to proper turbo selection and tuning. “That 14cm turbine housing on that turbo doesn’t work well for automatics without a bunch of horsepower to drive the ’charger,” says Bill Allen, the man in charge at Source Automotive in Clackamas, Oregon. Bill says Source’s technicians see combinations similar to yours “go sideways too many times,” as shops generally do not give the customer much education on the driving style changes necessary when a larger turbine housing is installed on the turbo. “The larger diameter you go on the housing, the more fuel you need to properly drive the turbo—especially at higher elevations, as the lack of air density at higher altitudes makes the charger spool slower,” Bill says. He always recommends 5.9L 12-valve customers “size down” on the housing to maintain good driveability. “On most 5.9L Cummins/automatic transmission applications, we suggest using a 12cm housing to maintain good low-end and towing ability,” Bill says.


QUESTION: When I noticed white smoke blowing from my Ford F-250’s exhaust, I shut the engine down right away. I have read enough about that condition to know the EGR cooler failed. The truck has 190,000 miles, with about 120,000 of that distance covered on a warranty-replacement 6.0L Power Stroke engine. The oil looks clean, and I think I caught the problem in enough time to not hurt anything. I want to keep the truck as close to stock as possible, so is an upgraded EGR cooler with a filter and a replaced stock oil cooler a good fix? Is there one EGR cooler that performs better than another? Are there any other items I should address while getting these repairs/upgrades done?
Shawn Littleton
via email
Photo 4/5   |   A blown EGR cooler has better than a 90 percent chance of also compromising the integrity of the head gaskets on 6.0L Ford Power Stroke engines. The best and cheapest fix in the long run is to replace the head gaskets along with a stock oil cooler and aftermarket tube-type EGR cooler.
ANSWER: Your diagnosis and quickly getting the truck off the road was a good call. The bad news about EGR coolers is when they let go, the coolant leaking into the cylinders usually damages the head gaskets. “We see head-gasket failure rates of about 85 to 90 percent when the EGR cooler is blown,” says Mark Gotchall at Oregon Fuel Injection. “There’s about eight hours of overlap in additional labor if the oil cooler and EGR cooler are replaced, and then the head gaskets have to be replaced. For that reason, we highly recommend customers have the coolers and head gaskets replaced at the same time.” Mark says coolant flowing into the cylinders increases the combustion pressures to the point the head gaskets are almost always compromised. Installing a new stock oil cooler is fine. “With a coolant filter, the OEM-style oil cooler will last 150,000-plus miles,” Mark says. Several other diesel shops we spoke with that service a lot of 6.0L Power Strokes say that in your situation, replacing the stock fin-style EGR cooler with a round-tube version, such as the unit offered by Bullet Proof Diesel, is the best move. “The round-tube designs are superior to stock,” explains Kenneth Tripp at Tripp Trucks. “And they are available from quite a few manufacturers. The year of the 6.0L will determine whether or not replacing the head gaskets and installing ARP head studs is also recommended, as the ’03-to-early-’04 6.0Ls are less likely to blow head gaskets than the ’04½-and-newer engines.” Kenneth agrees it is better to spend the extra money for new head gaskets when replacing a blown EGR cooler than having to get a new cooler installed only to find out later on the gaskets are shot. Many other Power Stroke experts agree.


QUESTION: I’m ditching my 10-year-old Ford F-150 daily driver for a ’17 F-350 that will be the rolling showcase of my new landscape design business. I want the truck to turn heads, yet I still want to keep it functional as my primary business vehicle and tow rig. All my trucks have been kept pretty stock—but not this time. What effect will a 6-inch lift and 37-inch tires have on the new truck compared to it being bone-stock? I’m also having a Warn 16.5 winch, matching heavy-duty bumper, and LED lightbars installed. I don’t plan on doing any mods to the 6.7L Power Stroke engine until it’s out of warranty.
Brad Bishop
Via email
Photo 5/5   |   Lift kits, taller tires, and other upgrades can really improve the appearance of a diesel-powered 4x4 pickup. The downside is those modifications may have an adverse effect on several vehicle dynamics, including a drop in fuel mileage and braking performance.
ANSWER: Changing the stance with a moderate lift kit, bigger tires, and a winch/bumper combo will definitely make your new Super Duty stand out and provide a lot more ground clearance. However, the modifications will affect performance, from acceleration and braking to handling and fuel economy. The effects might not be big, but they will be seen and felt. First, let’s look at fuel economy. The lift raises the body 6 inches higher, and the jump from the stock LT275/65R18 tires to 37-inch rubber adds another 2.5 inches to that new height. The higher the body, the greater the amount of drag from the wind moving over and under the truck. Drag only really comes into play at speeds more than 60 mph, and the gain in “the coefficient of drag” is exponential, in other words drag increases in proportion to the square of speed. Put bluntly, the faster you go, the more fuel it takes to maintain a certain speed—and the bigger the lift and wider/taller the tires, the higher the wind resistance (drag). Drag also comes from a wider tire with more surface coming in contact with the road. Then there’s weight, both “sprung” and “unsprung.” The sprung weight is the added weight of the lift kit, winch and bumper, and such. The unsprung weight is everything hanging below the springs. Pushing more weight down the road creates more resistance and burns more fuel. It also takes more power to turn the taller, heavier rubber. Taller tires also change the final-drive ratio. The ’17 Super Duty has a 3.55:1 axle ratio, which is the equivalent of a 3.07:1 ratio when running 37s. Having this “taller” final-drive axle ratio results in considerably slower low-end acceleration, with lots of lugging at freeway speeds unless you increase the engine’s power output. A gearing change really becomes prevalent when towing or hauling a heavy load. Combine the extra drag, weight, and effective axle ratio, and highway fuel economy will drop—by as much as 5 mpg at cruising speeds unloaded and 1 to 3 mpg towing trailers. Braking is also affected by a big lift, because the stock brakes have a harder time handling the increased rolling mass of the bigger tires, which can be as much as 30 pounds per tire. The taller a truck is, the higher its center of gravity. The higher the center of gravity, the more body roll the truck will experience when cornering. Also, a taller truck brings other issues, such as getting fifth-wheel and gooseneck trailers hooked up because of the increased hitch height. Just be aware there are a number of other items that also need to be changed to retain stock performance and handling. We recommend having the differentials re-geared to 4.11:1 when the lift is installed, which should keep the 6.7L running the same rpm at 60 mph as it would have before adding the taller tires. Install beefier anti-sway bars to help keep the higher center of gravity under control and upgrade the brakes to support stopping with the bigger tires. Also, don’t skimp on shocks—spend the money on the best ones you can find.


QUESTION: I’ve been having a hard time getting my ’12 Ford F-250’s 6.7L Power Stroke engine to start. Sometimes it starts within one or two cranks, while other times I can crank it for a couple of minutes before the engine fires. And it also seems to be running rough. I scanned the ECM for diagnostic trouble codes, and DTSC P1291 was detected. I’ve replaced the fuel filters, drained the water separator, and added a fuel conditioner. The problem is still there.
Rick Hollister
via email
ANSWER: According to the diagnostic trouble codes, P1291 is “Injector High Side Short To GND or VBATT Bank 1.” What Ford says it really points to is an internally shorted fuel injector, which Ford says can happen when diesel-exhaust fluid gets into the fuel tank—or fuel gelling—triggering P1291 or P1292. We suspect DEF was somehow poured into the fuel tank. Ford TSB 11-10-10 covers this, and the service procedure is to remove the filter that’s mounted on the fuel conditioning module and let it air dry for a couple of hours. If the filter and/or bowl shows a white crystalline residue, the fuel has DEF in it. This requires replacing the “complete high-pressure fuel system and diesel fuel control module (DFCM) along with flushing the entire base fuel system. If there’s no white residue, Ford recommends removing the valve cover on bank 1 and checking the continuity between each of the injector pins and bodies (#1, #4, #6, and #7). If one is bad, replace it. If all check out according to the Powertrain Control/Emission Diagnostics (PC/ED) manual, then Ford recommends replacing all the injectors and the injector-return hose. DEF in the fuel is a huge (and costly) no-no!