Guts and Gears: How to choose a transmission for heavy hauls - Truck News (2024)

Guts and Gears: How to choose a transmission for heavy hauls - Truck News (1)

TORONTO, Ont. — All the power in the world won’t get you anywhere if your transmission can’t manage it properly. Startability and gradeability are the two key factors in powertrain spec’ing, which means getting the power to the wheels safely — without wrecking the driveline — and having several ratios to keep the truck moving while climbing. In applications where the grades aren’t too severe, 10- and 12-speed transmissions can work even with the heaviest legal loads. When you start pulling 7, 8 and 9% grades with more than 62,500 kg in tow, you simply need more gears.

In bygone days, this was the realm of the 5×4 and 6×4 duplex transmission. These were necessary before we had 2,050 lb-ft engines and 18-speed high/low splitter transmissions. The main gearbox had large steps between the gears, and the auxiliary transmission provided the incremental steps between the main gears. The modern 18-speed transmission, manual or automated, offers closer steps between the gears as well as high and low range shifts and a direct and overdrive split in each gear. The result is a transmission with fewer ratios overall — with more even steps between the gears — but much easier to operate.

We can get by with fewer gears today thanks to the way engines have evolved, specifically when it comes to changes in their torque curves. Prior to 2000, most engines had distinct peaks to their torque curves, which limited peak torque to a pretty narrow range, sometimes less than 100 rpm. To allow the engine to operate at peak output, we needed lots of gears to keep the engine speed at or close to peak output. Gradually those curves flattened out and torque output increased so trucks could stay in certain gears longer. Today’s torque curves are more like plateaus — flat and broad, often extending through a range of 400 or 500 rpm and sitting way down low in the rpm range. Rather than downshifting through two or three gears when climbing a grade to stay at or close to peak torque, we now need only one or two gears.

In Canada, the preferred multi-speed transmission for heavy haulers seems to the Eaton 18 speed. But of you want a high-horsepower engine, you’ll need to go with either Detroit’s DD16 or the Cummins X15 performance variant. For those engines, you’ll need something from Eaton.

For years Pierre Aubin, owner of L’Express du Midi, Delson Transport, and Transport Audet of Ste-Catharine, Que., has been spec’ing Eaton 18-speeds behind his 600-hp Cummins engines. Between the three companies, he runs more than 100 B-trains and four-axle flatbeds with payloads of 41,000 and 38,000 kg, respectively. They’re all operating in northern Quebec and on that province’s notorious Cote du Nord, between Sainte-Anne-de-Beaupré and Sept-Isles.

“That’s no place for an under-spec’d truck, let me tell you,” Aubin says. “You need all the gears and the close ratios on those roads. They are nothing like American highways. When you get to the top of that first hill, you’re looking into the eyes of God.”

Most of his 18-speeds are manuals, by the way. He has a few UltraShift Plus automated 18’s and few automated transmissions in his straight-truck tanker fleet. “I do not see the value in spending an additional $8,000 for a less-reliable transmission,” he says. “Those automated transmissions are a pleasure to drive, I’ll admit that, but when they break down they leave you with no options but to call a tow truck.”

In contrast, many other Canadian B-train fleets claim they are doing just fine with automated manuals. Winnipeg-based Paul’s Hauling is primarily a fuel hauler using B-train tankers. The company operates throughout Ontario and the four western provinces as well as on the winter roads around Thompson in northern Manitoba and Pickle Lake in northern Ontario.

The company’s powertrain spec’ might seem surprising. The newer trucks in the fleet are all 13-litre engines at 1,850 lb-ft and 500 or 505 hp. The transmission spec’ includes Eaton UltraShift Plus and Mack mDrive, and the most recent delivery from Freightliner included the DT12 transmission.

“The latest bunch of Cascadias we ordered from Freightliner were equipped with the DT12,” says Trent Siemens, director of maintenance at Paul’s Hauling. “We had been testing a few for about a year and Freightliner was watching them closely. They have now approved the transmission for our application with the DD13 engine at 505/1,850.”

Daimler’s current brochure shows the maximum gross vehicle weight for the DT12 is 130,000 lb. (58,500 kg), so this application suggests it’s capable of even more with engineering approval.

“We do not tell the OEMs specifically what we want. They give us what they feel is best for the application given our weight and terrain and the rest of our operating conditions,” Siemens says.

The fleet also took recent delivery a few Peterbilts with Paccar MX13 engines at 510/1,850 and Eaton UltraShift automated 18-speeds. Later this year they will take delivery of some Mack Anthems with similarly spec’d MP8 engines and the new 13-speed mDrive HD transmissions.

While smaller-displacement engines and proprietary “on-highway” transmissions keep turning up in fairly demanding applications, don’t count on seeing many of them in really heavy haul applications like the fleets that haul overweight loads with specialized equipment. For that crowd, it’s Eaton’s RT-series 18-speed manual transmissions or the Ultrashift Plus MXP automated 18-speed — or even a two-stick 5×4 or 6×4 setup.

With 100-ton loads, the need for gears and tons of torque and horsepower are pretty obvious. While much of the on-road driving portion of those trips might be done with a lesser setup, it’s often the last few miles of a trip that dictate the spec’, says Rod Olyowsky, operations manager of Regina-based heavy-hauler Cara Dawn Transport.

“More than half or our revenue comes from loads weighing 100,000 lb. or more,” he says. “We haul all over North America, but the most challenging jobs see us hauling into mine sites in southeastern British Columbia. They usually aren’t located a few miles from a freeway off ramp. They are often at the top of a 10- or 20-mile long 9% grade.”

Cara Dawn runs mostly tri-drive tractors in the west with 600-hp/2,050 lb-ft engines mated to 18-speed transmissions, “We still have a few duplex 5×4 transmissions as well,” says Olyowsky. “Sometimes even those are barely enough.”

Many of the older drivers who work in that sector are leery of the automated manual transmissions, but the UltraShifts are making their way into the business.

“There’s a big difference between 140,000-lb. GVW and 280,000 to 300,000-lb. GVW on a 9% grade,” says Olyowsky. “The drivers prefer to be in control of what the equipment is doing.”

Of course, a lot of drivers said that about 80,000-lb. GVW trucks when the Eaton’s AutoShift first emerged 20 years ago. It’s taken some time, but now many of those drivers won’t leave the yard with anything but an automated transmission.

Guts and Gears: How to choose a transmission for heavy hauls - Truck News (2)

More options than ever

Canadian fleets that operate six-and seven-axle combinations now have transmission and engine choices they may not have considered in the past. Transmission choices for really heavy applications are still quite limited, but the mid-weight market between 47,000 and 57,000 kg is now opening up to the 12-speed offerings. Gross weight may be less of a factor than it previously was, but the terrain you operate on will still be the determining factor for your transmission spec’.

Along with the traditional 18-speed offerings from Eaton, we now see Volvo’s I-Shift and Mack’s mDrive HD providing additional ratios for heavy haul and severe service. These offer up to 14 forward gears with astonishingly low creeper ratios for specialty applications like pouring curbs and sidewalks by concrete mixers. They are also more than capable of handling some high-GVW on-highway applications if not 100,000-kg loads of mining equipment on the side of a mountain.

Transmissions don’t care which engine is producing the torque, so with ratings mostly exceeding 2,050 lb-ft, most of the 12-speed transmissions can now handle big power. Neither Volvo or Mack offer an engine producing more than 1,860 lb-ft, so there’s obviously some redundancy in those transmissions. Daimler’s DT12 is also rated for 2,050 lb-ft, and it’s allowed in applications up to 130,000 lb. (58,500 kg) with a dual-plate clutch and approval from engineering.

Here are a few choices worth considering.

Allison TC10

Speeds: 10 forward / 2 reverse

Torque rating: 1,850 lb-ft

Gear Ratios

Overdrive: 7.40 – 0.86

Dry weight: 1,074 lb. / 487 kg

Detroit DT12

Speeds: 12 forward / 4 reverse

Torque Rating: 2,050 lb-ft

Gear Ratios

Direct Drive: 14.93 – 1

Overdrive: 11.67 – 0.78

Dry Weight 518 – 639 lb. / 233 – 287 kg

Eaton UltraShift Plus MXP

(Multipurpose Extreme Performance)

Speeds: 18 forward / 4 reverse

Gear Ratios

A-ratio: 16.70 – 0.73

B-ratio: 19.73 – 0.73

Torque rating: 1,650 – 2,250 lb-ft

Dry weight: 978 lb. / 444 kg

Eaton RT-18 Manual

Speeds: 18 forward / 4 reverse

Gear Ratios

B-ratio: 14.4 – 0.73

Torque rating: 2,250 lb-ft

Dry weight: 716 lb. / 324 kg

Mack mDrive HD

Speeds: 12, 13, 14 forward / 2 reverse

Torque rating: 2,060 lb-ft

Gear Ratios

Direct Drive: 19.38 – 1

Overdrive: 17.58 – 0.78

Dry weight: 687 lb. / 312 kg

Mack Maxitorque ES manual

Speeds: 18 forward / 3 reverse

Torque rating: 2,100 lb.-ft.

Gear ratios: 16.42 – 0.71

Dry weight: 798 lb. / 359 kg

Volvo I-Shift

Speeds: 12, 13, 14 forward / 2-6 reverse

Gear ratios: 11.73 – 0.78

Torque Rating: 2,300 lb-ft

Dry weight: 720 / 324 kg

Guts and Gears: How to choose a transmission for heavy hauls - Truck News (2024)


What is the best transmission for a heavy truck? ›

Planetary Automatic Transmissions

They are known for their ease of use, smooth operation, and ability to adapt to varying driving conditions. Planetary automatic transmissions are commonly used in heavy-duty trucks where driver comfort, convenience, and reliable performance are prioritized.

What's the best automatic transmission for a semi truck? ›

Transmission Comparison Table
Freightliner CascadiaDetroit DT12Smooth shifts, fuel efficiency, predictive cruise
Volvo VNL SeriesVolvo I-ShiftRapid gear changes, advanced fuel management
Kenworth T680PACCAR TX-12Reliable, optimized for heavy hauling
Peterbilt 579PACCAR TX-12Durable, driver-friendly
1 more row
Feb 29, 2024

What is the strongest transmission? ›

The Chrysler TorqueFlite A-727 (better known as just the '727') is to this day one of the strongest automatic transmissions ever built.

What is the most common transmission in a truck? ›

The move away from manual transmissions is dominating the Australian truck market, and percentages are growing. This year alone, over 80 per cent of all car-driver's licence truck models sold (up to 4500kg GVM) have been specified with a two-pedal automatic or automated manual transmission (AMT).

What is the most reliable truck transmission? ›

The Allison 1000 transmission, equipped in 2001 to present Chevrolet and GMC trucks of all types, is the single King of the transmission world.

What is the best transmission in a diesel truck? ›

Read on to see which ones we recommend for your specific brand.
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  • Quick-Shifting. ...
  • Five-Speed TorqShift: 2003-2010 Fords. ...
  • Elite 5R110. ...
  • Six-Speed TorqShift: '11-present Fords. ...
  • Allison 1000: 2001-present Chevy and GMC's. ...
  • Built Allison Options. ...
  • Turbo 400: Old Tech That Still Works.
Oct 13, 2016

What truck has the best transmission for towing? ›

Top Transmissions for Towing

Ford 10-Speed Automatic Transmission: This transmission is found in many of Ford's heavy-duty trucks and is designed to handle up to 475 horsepower and 1,050 lb-ft of torque. It also features tow/haul mode and a built-in transmission cooler.

What are the disadvantages of a semi-automatic transmission? ›

AMTs combine the fuel efficiency of manual transmissions with the shifting ease of automatic transmissions. Their biggest disadvantage is poor shifting comfort due to the mechanical clutch being disengaged by the TCU, which is easily noticeable as "jolting".

Which automatic transmission is best? ›

DCT Dual Clutch Transmission is the most advanced automatic transmission type you can have. Here, 2 clutches that operate 2 sets of gear ratios. The computer automatically selects the next gear using the alternative clutch. This results in a negligible difference during gear shifting.

What is the number one enemy of an automatic transmission? ›

The number one enemy of automatic transmissions is heat. Nothing will destroy an automatic transmission faster than allowing it to overheat. To help reduce that heat, nearly every automatic transmission has a transmission cooler, usually mounted in one of the radiator tanks.

Which type of transmission lasts the longest? ›

Manual transmissions require less servicing to remain functional and don't need the same type of oil as an automatic transmission. Cars with a stick-shift usually last longer than an automatic of the same make and model.

Who builds the strongest 4L60E transmission? ›

PerformaBuilt Transmissions is run by car guys and they've learned what makes a transmission handle big power and what's just a waste of cash. Their Stage 2 Pro Race transmission can handle gobs of power while their Invincible Black Edition 4L60E trans can support over 1,000 ponies.

What transmission is best for a 454? ›

You can get a really good aftermarket transmission from Tremec or Gearstar or you can find either a 350 or 700 automatic transmission out of a GM vehicle. Muncie M22, Tremec T-56 if you want overdrive, TH400 if you want an automatic, TH700R4 if you want an automatic with overdrive. If it were me, I'd prefer the T-56.

Which transmission is more reliable? ›

Manual transmissions are more reliable than automatics. When automatic transmissions go wrong, repair costs can stack up into thousands of dollars. Manual transmission cars, on the other hand, have a much lower chance of failure, and if something does go wrong are usually much cheaper to fix.

What brand has the best transmission? ›

What Is the Most Reliable Automatic Transmission?
  • Lexus 8-speed automatic. ...
  • Porsche PDK. Porsche. ...
  • Audi S-tronic. Audi. ...
  • Mercedes-Benz 7G-Tronic. Mercedes-Benz. ...
  • BMW 8-speed automatic. ZF Friedrichshafen AG. ...
  • Christian Flores · Public domain. Ford 10R80. ...
  • General Motors Hydra-Matic 10-speed. General Motors. ...
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What is the best transmission for loader work? ›

Hydrostatic Transmission

Hydrostatics operate like automatic transmissions in cars. This transmission is efficient, smooth, and easy to operate. They are optimal for loader work and any task where the implement does not require it to be maintained at a constant speed. Speed control is another advantage.

What is the best transmission for a dump truck? ›

Max GCW. Overall, the GCW and material type that you're hauling are going to affect your transmission choice. For example, if you're hauling more than 110,000 lbs., it will probably be best to go with a 13- or 18-speed transmission over a 10-speed so you have better performance.

What is the most efficient type of transmission? ›

Manual transmissions have the highest efficiency due to their inherently low parasitic losses. Because they are usually splash-lubricated from gears spinning in the oil sump, manual transmissions usually do not require the oil pump or forced cooling that most automatic transmissions require.


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