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Diesel tech Q&A

You’ve Got Questions, We’ve Got Answers

Bruce W. Smith
Oct 31, 2019
Aisin vs. 68RFE
QUESTION: I've been thinking about buying a single-rear-wheel '12 Ram 3500 with the high-output 6.7L Cummins engine, and I'm wondering if it comes with the Aisin six-speed automatic transmission. Also, what's the difference between the Aisin and the regular six-speed transmission?
Willy Sandborn
via email
Photo 2/6   |   The Aisin AS69RC six-speed automatic transmission (below) is standard on the Ram 3500 with the High Output 6.7L Cummins engine. Back in 2013, the heavy-duty truck transmission replaced the 68RFE (top) when the H.O. Cummins was first offered. Ram's Heavy Duty brochure touts the H.O./Aisin package as being built to handle "the rigors of commercial-grade assignments."
ANSWER: No, the '12 Ram 3500s were not available with the Aisin automatic. The AS69RC, aka Aisin, six-speed transmission is an optional gearbox that was first introduced for the '13 Ram 3500 Heavy Duty and chassis-cab models. That Aisin is a heavy-duty transmission that replaced the AS68RC made for Dodge by the Japanese gearbox manufacturer Aisin Seiki in collaboration with BorgWarner. Prior to the '13 model, Ram used the AS68RC in the company's Commercial Truck (chassis cab 3500 to 5500), beginning in 2007 when the 6.7L Cummins powerplant made its debut. To handle the '13 engine's higher torque, the AS69RC emerged. (Ram says the AS69RC has a 64 percent higher input torque capacity than the AS68RC). Compared to the earlier-model Aisin, the new one has a more robust input shaft, more clutches and larger clutch hubs, additional pinion gears in all the planetaries, the deletion of the F1 sprag clutch for First and reverse gears, a more aggressive Tow/Haul mode, and so forth. The Aisin also has numerous PTO options. In short, the 400-pound Aisin is a stout medium-duty, electronically controlled six-speed. In comparison, the Chrysler 68RFE six-speed automatic is a light-duty-pickup transmission that weighs about 260 pounds and isn't set up to use a PTO. The 68RFE is a well-designed and strong transmission with gear splits suited to the normal load-moving tasks faced by heavy-duty Ram diesel pickups. But it's not strong enough to handle the high-output Cummins if one is towing at or near the maximum rating of a Ram 3500 day in and day out. The 68RFE is not nearly as robust as the Aisin in any way, shape, or form. They are two totally different transmissions. While the Aisin's overall ratio spread is 3.75-0.63, the 68RFE's is only 3.23-.0.63. The difference is the Aisin has a much deeper First (3.75:1) and Second (2.0:1) to maximize the 6.7L's torque delivery for more low-end pulling power. From a service standpoint, the Aisin requires fluid changes every 30,000 miles and filters at 60,000 miles, whereas the Chrysler 68RFE requires fluid and filter every 120,000 miles in "normal" operating conditions and 60,000 miles in "severe" uses. The bottom line here is: If you are using your Ram 3500 for "commercial" hauling and/or towing applications where trailered loads are more than 18,000 pounds, the Aisin AS69RC is the automatic transmission for you. But for the rest of the Ram 3500 6.7L pickup owners, the Chrysler 68RFE will do the job as intended.
 
Shiftless 5R110
QUESTION: We have an '04 Ford F-350 6.0L with around 280,000 miles on it. Recently, after parking the truck for the night, it would not move the next afternoon (regardless of which gear in the transmission was selected). Fluid was a bit low with a slight "burnt" smell, so I topped it off, scanned the ECM for engine and transmission diagnostic trouble codes, and found none. Line pressure all seemed good. We never noticed any noises or slipping whatsoever. We use a mild (60hp) towing calibration. So what are your thoughts? Input shaft? Torque-converter splines? A bad sensor or wiring?
Allen
via email
ANSWER: Does it roll with the transmission in Park? If it does, then there's an issue inside the transfer case. If it doesn't roll with Park selected, then there's a mechanical issue inside the transmission. As one of our Ford transmission contacts told us, "There's nothing electronic that would cause such an issue." Realize that not all code readers can retrieve the entire group of diagnostic trouble codes associated with the 5R110 TorqShift. So make sure the scan tool you are using is indeed capable of reading the codes that point to your transmission issues. The Ford 5R110W ('03-to-'10) Transmission Service manual states the following: The 5R110W is unique in that it lacks a typical valvebody. Instead, the 5R110W contains a "solenoid body," which contains a series of seven electronic shift solenoids. In lieu of a hydraulically controlled shift system, the ECM commands shifts and controls line pressure by means of these shift solenoids. A problem that is not mechanical (i.e. worn/damaged mechanical parts) is almost always a solenoid or sensor problem. Both electrical and mechanical problems are generally detected and a fault code is set. When a transmission code is triggered, the Check Engine light will not illuminate in the dash. Instead, the ECM will alert a driver to a transmission fault code through the Tow/Haul light on the transmission shifter. If the light begins flashing, a transmission fault has been detected and can be retrieved with a proper diagnostic tool. Another point of interest of the 5R110 is although Ford advertises TorqShift as a five-speed, it really is a six-speed. The way it's designed is to use Overdrive in First, Second, and Third gears like this: First, First OD (Second), Second (Third), Third OD (Fourth), Third (Fifth), and Third OD (Sixth). But because Second OD (Fourth) has a gear ratio of 1.09:1 and Third (Fifth) has a ratio of 1:1, making that shift is meaningless under normal operating conditions. But in the extreme cold, below 5-degrees F, it will shift into the slightly lower-ratio Second OD (Fourth) and then Third OD (Sixth) until the transmission fluid gets up to a certain operating temperature. In some instances, the transmission will also downshift from Fifth to Fourth. But there's never a Fourth-to-Fifth upshift because the ratios are almost the same. Some monitors, such as the Edge CTS, count gear shift "events" and not actual gear changes. So what you are seeing and feeling is five shifts and then torque converter lockup—not six actual gear changes. It is also important to note Ford recommends that transmission have a full service every 30,000 miles, which includes replacing the fluid and both external and pan filters.
 
Tire Pressure
QUESTION: I just stepped up from a '13 Ram 1500 with a Hemi engine to an '18 Ram 2500 that's powered by the 6.7L Cummins. The truck's primary use is to tow stock and equipment trailers around the ranch and pull our new 34-foot toy hauler on days off. Which tire pressures should I use for the best ride when I am not towing? The sticker on the doorjamb only states to use 60 psi in the front and 80 psi in the rear. But my wife says the truck rides like a rock when we aren't towing.
Gary Brown
via email
ANSWER: Always abide by the vehicle manufacturer's "cold" tire-inflation pressures, as shown on the B-pillar placard, when trailering. Those are the tire pressures the engineers in charge of vehicle dynamics (ride/handling/safety) determined are best suited to handle the rated maximum trailer/load capacity with the tires that came with your truck. What many owners of single-rear-wheel heavy-duty diesel rigs have learned is that dropping the inflation pressure down to 50 psi front/rear on those E-rated stock tires provides a nicer ride when driving around without a trailer. If you change to different tires later, remember the cold-tire inflation pressure must not exceed the maximum inflation pressure molded into the tire sidewall. It's also important to stay with E-rated tires if you are towing trailers anywhere near your Ram 2500's maximum-tow ratings. They have the highest load-carrying capacity.
 
Electrical Gremlins
QUESTION: Help! Electrical gremlins attacking my '12 GM pickup are giving me fits. The engine skips a beat or shuts down every once in a while—and it is becoming a little more frequent. It can happen anywhere, anytime. There are no diagnostic trouble codes, either. It seems to be a totally random deal. There is also a warning on the dash to service the trailer—even when I'm not towing one. Are there any common problems I should look into first?
Wes Miller
via email
ANSWER: Random electrical gremlins are the worst—especially when there are no trouble codes to help make diagnostics a little easier! It sounds like there may be a wire rubbing against something and shorting out. We recommend you take a serous look at the ECM wiring harness to make sure it hasn't started to come loose and that there isn't a bare spot making contact with a metal brace, pipe, bolt, clamp, or some other part. On some of those 6.6L Duramax LML engines, owners are finding the wiring harness that runs over the top of the engine rubs on the air-conditioning line enough to wear through the sheath and into some of the wires inside. The right bump or vibration can cause an intermittent short—or other odd and frustrating electrical issues. Making repairs using high-temperature automotive wiring-harness loom (cloth tape, or slipping split loom over the affected area) takes care of the problem. If you find a wire harness that's rubbing on something, zip-tie it to some other part that keeps it from harm's way.
 
Winter Fuel Additive
QUESTION: Do you recommend diesel fuel additives during the winter months? If so, which one is best and how often should I use it? I just purchased a '19 GMC 2500 Denali and live in northern Nebraska.
Stevenson
via email
Photo 3/6   |   Fuel additives can play an important role during the winter months for diesels that operate in subfreezing temperatures. Not only do they add lubricity and reduce fuel-quality issues, but fuel additives can also increase the cetane rating for easier cold starts.
ANSWER: Some diesel purists say never run additives of any sort, while others consider them as vitamins for the long-term health of the engine. We think they improve overall performance and help with preventive maintenance of the entire injection system during winter months. But it's important to follow the instructions for using fuel additives (printed on the container) to the letter. Before buying additives, read your new truck's owner's manual and "Duramax Diesel Supplement" to make sure GM is "OK" with the use of fuel additives. Note: On page 46 of the "2018 Duramax Diesel Owner's Manual Supplement" it says the use of "Aftermarket diesel fuel additives, which contain alcohols, organo-metallic additives, or water emulsifiers" may cause engine damage and "may void the vehicle warranty." That aside, the additive manufacturers have their own warranty coverages listed on the containers and on their websites that should alleviate any of those types of concerns. Fuel additives with a "cetane booster" are optimal when living in regions where winter temperatures may be below freezing for weeks or months at a time. Alec Hembury, at Industrial Injection Diesel Performance, is of like mind. He says Industrial's branded Deuce Juice Fuel Additive "adds lubricity to the fuel system that low-sulfur fuel has taken away. The added lubricity increases fuel components' service time span by 15 to 50 percent, and it improves reliability as well as performance, since the injection system can operate more smoothly. Adding cetane to the fuel helps it burn hotter, which increases power and fuel mileage. In addition to increasing lubricity and cetane, Deuce Juice cleans the fuel system and disperses any water that may get in the system." Mark Gotchall at Oregon Fuel Injection recommends Stanadyne Performance Formula. "Fuel quality varies from area to area across the U.S., and even from the same station," Mark says. "So a good diesel-fuel additive with cetane boost means less smoke and more power. In a DPF-equipped vehicle, that means fewer particulates and fewer regeneration cycles for better mileage." Diesel additives also help prevent the fuel from gelling when temperatures drop below freezing. A link to some informative reading about cetane can be found on our website: trucktrend.com/how-to/expert-advice/1704-cetane-numbers-how-diesel-fuels-biggest-unknown-affects-your-truck/
 
Slipping E4OD
QUESTION: You guys have probably had this question asked dozens of times in the past, but I didn't see it going through a couple of years of back issues. I inherited my gramps' '96 Ford F-250. The truck runs great but recently the automatic transmission slips going into Third gear and then the Overdrive (O/D) light starts flashing. I checked for diagnostic trouble codes using the Edge Products CTS monitor and found a transmission-slip fault code. I also checked the fluid—it's a little dark and smells funky. Your thoughts?
Wilson
via email
ANSWER: If the transmission is only slipping in Third gear—and the fluid is dark and smells burned—then unfortunately a rebuild or replacement is probably necessary. Once the clutches in the packs start slipping, they don't last long. When you pull out that transmission and have it rebuilt, we suggest getting a performance-rebuild kit that has the upgraded parts shared with the 4R100. A good set is the E4OD Mega Monster from Monstertransmission.com. Such performance-rebuild packages have better clutches, steels, bearings, seals, rear sprag, and line-pressure modifications to better accommodate the bigger tires and slight power boost of your rig's 7.3L engine. We also recommend a billet torque converter matched to the 7.3L's power curve. Sometimes you can find rebuilt "Stage 2" performance E4ODs on the Internet for nearly the same price as it would cost to have one rebuilt locally.
 
D-Max Pistons
QUESTION: My '13 GM pickup had just passed 121,000 miles when several pistons cracked. I was stupid: Wide-open throttle (WOT) while passing a line of slow-moving cars on a grade, with a loaded equipment trailer in tow. I wasn't paying attention to EGT, and the engine paid the price. The previous owner had the 6.6L Duramax engine hopped up with a tune, new turbo, and 60-percent-over injectors installed at 93,000 miles, and I bought it with 107,000 miles. Which pistons would you recommend that will stand up better than the stock pieces?
B. Chamberlain
via email
Photo 4/6   |   Owners rebuilding their diesels for higher-than-stock output, like this 6.6L Duramax that suffered cracked original pistons, might consider replacing the stock slugs with Mahle Motorsports' Performance Cast Pistons coated with the optional ceramic Thermal Barrier Coating, which adds a layer of protection against hot spots and high EGT.
ANSWER: A heavy right foot at the wrong time with a hopped-up Duramax has been known to do that. One can't go wrong with Mahle Motorsports when it comes to pistons for a truck like yours. The Mahle Performance Cast Pistons, coated with the optional Ceramic Thermal Barrier Coating, are our first choice. Mahle's pistons are meatier— especially around the wristpin area that's said to be a weak point that causes stock pistons to crack in higher-than-stock-horsepower applications. Mahle says this version of replacement pistons is ideal for 400 to 1,000hp "street/strip" daily driver/work truck applications. It also notes the pistons drop compression .5 to 1.5 points, which "allows more flexibility for high-output tuning." The Thermal Barrier Coating, which Mahle just started offering in 2019, reduces heat transfer, keeps the pistons cooler, and helps protect the crown of the piston from forming hot spots—all important factors when cylinder pressures and EGT are being pushed to the upper limits during heavy-footed towing situations. It would also be prudent to have the injectors tested to make sure none contributed to the piston failure(s) and the rods checked by a machine shop for trueness. Also make sure you note the "IQA" or "trim code" of each injector and which cylinder it came out of so there are no balance-rate, no-start, or rough-idling issues. The same injector needs to go back into the same cylinder—or you will have to reprogram them to the ECM using a scan tool.
 
Turbo Concerns
QUESTION: The turbocharger on my '14 Ford F-250 failed at just 54,000 miles. Apparently, debris from the turbo has also damaged some valves. It requires a cab-off repair. The dealer is taking care of it for me because it's still under warranty. The truck is bone stock. I'm very disappointed that a truck that costs $60,000, has never been abused, and is meticulously maintained has these problems. Should the dealer look at other possible problems when they have it apart? I've heard yes and no.
Robert Yates
via email
ANSWER: Ford's 6.7L Power Stroke engines use the same Garrett variable-vane turbocharger (VVT) from '11-to-'14 models. The ceramic bearing in those early turbos is a weak spot and the primary culprit for the unit's failure. Ford changed turbo design in 2015. No Limit Fabrication offers a retrofit kit to put a '15 turbo on the earlier 6.7L. The system features a GT37 variable-geometry turbo like those Ford installed on the '15-to-'16 Power Stroke engines. That turbo uses a water-cooled, journal-bearing center housing that's much more heat-tolerant than the ceramic bearing in the earlier 'charger. The No Limit Fabrication kit costs around $2,500, includes all the parts needed to bolt in the new turbo, and retains all the stock emissions components. But it does require an ECM calibration. "Since this turbo is larger in internal components, it does spool slower than the original turbo in the '11-to-'14 trucks," according to the No Limit website. "This kit will require an aftermarket tuner that will make the slower spool-up less noticeable and adjust the settings to keep the fueling correct. "
 
Cummins Impellers
QUESTION: Are the Cummins 5.9L and 6.7L water pumps interchangeable? I want to get rid of the water pump with a plastic impeller on my '06 Ram 2500 with one that uses steel.
Sloan
via email
Photo 5/6   |   Cummins 5.9L and 6.7L I-6 water pumps are interchangeable as far as fit. If there are concerns about using a water pump with a composite impeller, there are several aftermarket brands that offer pumps with cast impellers. The 6.7L water pump flows more than the unit installed on 5.9L common-rail engines.
ANSWER: Yes, as far as fitment, the water pumps for those Cummins engines are interchangeable. But the seven-fin 6.7L Cummins water pump flows more than the five-fin 5.9L because it needs to supply enough volume to take care of the added cooling demands created by the 6.7L's EGR system. As odd as it may sound, a couple of years ago, a source at Murray, which manufactures water pumps, told us the old closed-vane water pump from the 12-valve 5.9L actually flows more than the open-vane style used in the common-rail 5.9L and 6.7L powerplants. The old closed-vane water pump does too good a job cooling in the colder climates, so Cummins went to an open-vane design on later generations. As for which water pump is better (i.e. more reliable)—pumps with composite impellers or cast iron—we don't see a difference if you are installing genuine Cummins parts. If a water pump with a composite impeller causes you concern, there are several sources to get a replacement made with a cast impeller. We know DieselSite offers them (PN DSI:WP:WPC), as does Diesel Power Products (PN CMNS-5473238).
 
WD Hitches
QUESTION: Is it necessary to use a weight-distribution hitch on diesel pickups when towing equipment trailers? Our company has four beavertail trailers that are used to haul backhoes, skid steers, and mini-excavators. We have two '16 Ford F-350s, a '14 Ram 2500, and a '20 Chevrolet Silverado 3500 on order.
Holroyd
via email
Photo 6/6   |   It is better to use a weight-distributing hitch when towing heavier trailers, like those hauling mini-excavators and skid steers, even if the vehicle manufacturer says they aren't needed. "WD" hitches, with the spring bars properly adjusted, provide better vehicle handling and load balance than just towing on the standard receiver shank and ball.
ANSWER: From a purely legal perspective, every tow vehicle must be "properly equipped" in order to avoid potential liability issues in case of a vehicle accident. Properly equipped means abiding by the vehicle-manufacturer's trailering guidelines as detailed in the truck's owner's manual and/or on the manufacturer's website under the RV & Trailer Towing guides. (Such information is usually found on the manufacturer's "commercial/fleet" website, not on the consumer side.) If that information says anything to the effect that a weight-distribution (WD) hitch "must" be used when trailered loads exceed X amount, then not using such a hitch places all liability on the business owner and the driver. Now, from a handling perspective, using a weight-distribution hitch when towing heavier trailered loads keeps the truck handling almost like it does without a trailer. A weight-distributing hitch, when properly adjusted, makes the truck steer, brake, and corner with the same ease and confidence as it does with nothing weighing down the rear. Regardless of the brand or model of your rig, if you have never towed a heavy trailer with the help of a WD hitch, you are in for a pleasant surprise. When we attended the media-drive programs of the Big Three's '20 heavy-duty pickup offerings, almost all of the equipment, ATV, and travel-type trailers being towed "on the ball" were set up with WD hitches. Even though Ford's and GM's '20 heavy-duty trucks are J2807 rated to tow their maximum without need of a WD hitch, all the trailers towing mini-excavators, skid steers and backhoes were fitted with them. And when we were at the Ram event, we asked if its Heavy Duty requires using WD hitches, and we were referred to page 412 of the (2019) owner's manual where it states: "If the gross trailer weight is 5,000 pounds or more, it is recommended to use a weight-distributing hitch to ensure stable handling of your vehicle. If you use a standard weight-carrying hitch, you could lose control of your vehicle and cause a collision. "

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