Advantages and Disadvantages of Dual Clutch Transmissions

Advantages and Disadvantages of Dual Clutch Transmissions

Last Updated August 30, 2019 | Meghan Drummond
Contents

Though a dual-clutch transmission is missing a clutch pedal, it’s hard to classify it as an automatic. While most automatic transmissions rely on either a torque converter or, if it’s a CVT, a system of pulleys, the dual-clutch transmission uses clutch plates, like a manual transmission. Because of the unique way a dual-clutch transmission is set up, if you drive it like it’s an automatic transmission, you’ll likely have a negative driving experience and can even seriously damage your transmission.

Understanding how a DCT functions and the advantages and disadvantages of this transmission style can help increase the longevity of the transmission and contribute to an improvement in overall driving experience.

Automatic vs Manual Transmission

The transmission of a vehicle is the component that’s responsible for transferring the power from an engine into wheel movement. Different styles of transmissions have different methods for doing this, but people primarily talk about transmissions in terms of automatic or manual. Though this is an overly simplistic view, it does relay the ability of the car to transfer gears on its own.

While manual transmission vehicles require the driver to disengage the clutch by way of a pedal, change gears, and then reengage the clutch, automatics typically handle gear changes on their own thanks to a torque converter. Though a torque converter and flexplate function similarly to a clutch and flywheel, these minor equipment differences lead to very different driving styles.

The next time you’re at a stoplight, look around. While automatic drivers have a tendency to “creep,” manual drivers prefer to wait until there’s enough room to put their car into gear before asking it to move. If you’re looking at an older manual vehicle, you might even see it roll back slightly (yet another reason not to tailgate). Because of how a clutch truly engages and disengages with an engine, the way in which manual and automatic drivers have to execute similar maneuvers is entirely different and determined by the needs of their transmission, so you can understand why it’s so important to understand which camp the dual-clutch transmission falls into.

Two views of a transmission

What Is a Dual Clutch Transmission?

Because it’s convenient to have an automatic transmission some of the time but most enthusiasts want a little more control of their gearing, manu-matics or semi-automatic transmissions, have become an increasingly popular style of transmission. Though they’re lumped into the same category, how semi-automatic transmissions accomplish the same goal takes a variety of different paths. One of those paths is the dual-clutch transmission.

A dual-clutch transmission is a transmission with at least two clutch discs, one for the even-numbered gears and one for the odd-numbered gears. Much like with a sequential transmission, the gears go in order, but instead of relying on the driver to tell it when to switch gears, the dual-clutch transmission swaps automatically. Almost all vehicles that have a DCT also have a manual mode though, and you can use paddle shifters to manually shift gears if you’d like. In that way, DCTs are a hybrid transmission system, not fully automatic or fully manual.

Some consider DCTs an automatic transmission because most of the time the gear shifts are automatic. Others consider it a manual because it still relies on a clutch plate and its gear shifting process (including the engine engagement and disengagement) is like a manual’s.

Really, the problem is that we’ve based so much of our understanding of what a car’s transmission is on the driver’s part of the equation that we’ve oversimplified a category that’s meant to be significantly broader. There are a lot of different types of transmissions, and saying that a continuously variable transmission (CVT) and a dual-clutch transmission are the same just because neither requires the driver to manually shift illustrates the uselessness of the distinction and why it’s hard to speak in absolutes about all transmissions that can automatically shift.

Wet vs Dry Dual Clutch Transmissions

Within the category of DCTs, one important distinction between different models is whether or not it’s a wet or dry clutch. More powerful vehicles require wet clutch dual transmissions, which just means that oil is used in order to help dissipate the heat that naturally builds up on the clutch plate.

Dry dual-clutch transmissions are more common and have several benefits as well. Dry clutches tend to be lighter, have less drag, and obviously are less likely to have spills or splash over. Unfortunately, they are also more prone to overheating.

Dual-Clutch Transmission Pros and Cons

The benefits of DCTs speak for themselves. Faster shifting, less loss of power, and more fuel efficiency.

The negatives are that there’s a bit of a learning curve to using them, they tend to have a little more jerkiness than the average driver is comfortable with, and they have a driving sensation that feels a lot like “turbo lag.” Until recently, there also weren’t very many vehicles available that offered a dual-clutch transmission, so selection was also incredibly limited.

Dual-Clutch Transmissions: Pros and Cons
Pros Cons
Faster Shifts Learning Curve
More Horsepower at Wheels Jerkiness
Improved Fuel Economy Few Vehicles Equipped with DCT
Freedom to Shift or Relax Expensive to Replace

Ford’s Previous DCT Transmissions: The PowerShift

Many are hesitant to try a DCT transmission due to Ford’s issues with dual-clutch transmissions in the past. Ford’s PowerShift DCT was seemingly plagued by problems, some caused by a leaky gearbox and some caused by as of yet unnamed sources that weren’t able to be remedied despite numerous transmission swaps and other costly maintenance procedures. These issues eventually led to a class-action lawsuit that affected many Focus and Fiesta owners.

Ford’s other vehicle with a DCT has had significantly more success. Ford’s GT operates with a seven-speed dual clutch transmission. Though manufactured by the same company as the Focus’ DCT, there have been no reported issues with the GT's transmission. Unlike the transmission manufactured for the Focus though the GT one has seven speeds and is a wet clutch system.

It’s fair to say that the Tremec that we’ll be seeing in the Shelby GT500 will be more similar to this transmission than to the one in the Focus.

A sporty orange Ford car zips along a road

Tremec Dual Clutch Transmission

The 2020 Shelby GT500 will come equipped with a Tremec seven-speed dual-clutch transmission. Mustang fans will recognize the name Tremec as being associated with some very solid transmissions. Tremec and Mustang have a long-standing relationship, and thus far without any class action lawsuits.

While the PowerShift was a dry clutch, the Tremec is a wet clutch that is “virtually dry.” Though it will still be heavier than a dry clutch, the wet clutch will allow for substantial cooling benefits, helping with some of the heat issues that seemed to affect the PowerShift negatively. It’s worth noting that the PowerShift had more problems if it was frequently driven on an incline, used in stop and go traffic, or if it was in a hot environment. These are all problems that were worsened by a majority of drivers operating the vehicles as though they were torque converter equipped automatics and also worsened by using a dry clutch, which is traditionally less good at dissipating heat. Just switching to a wet clutch should alleviate many of these issues. The virtually dry component though is meant to decrease drag, which is one of the primary downsides to wet clutches.

Tremec seems particularly pleased with the solenoids they’ve developed for this application, which are incredibly responsive despite their small size. In short, this DCT is a premium transmission designed to operate performance-oriented vehicles.

Drivers who are interested but wary about the longevity of a dual-clutch transmission can brush up on some driving strategies that can help extend the life of their transmission by alleviating stressors.

Three GT500s, in red, blue, and silver

How to Drive a Dual Clutch Transmission

Dual clutch transmissions really are a hybrid transmission system and as such there are a few tips that are going to be surprising and novel whether your daily is a manual or an automatic.

Stop Inching

One bad habit many have gotten into is inching up slowly when traffic is at a standstill or when they’re waiting on a light to change. By keeping your foot hovering above the brake you’re able to crawl forward in increments so small that over the course of a year you maybe gain six feet. Honestly, it’s a habit with few positive benefits anyway, but in a DCT it can actually harm the vehicle.

Manual drivers tend to wait until they have enough space to drive to actually throw their car into gear and have it be worth it, and that’s the attitude you need to adopt when driving a DCT vehicle. Otherwise, you’re “slipping the clutch” which can cause undue wear and tear on the clutch wheels.

A DCT transmission can inch forward, so if there’s a compelling reason to do so, don’t hesitate, but if you’re trying to take care of your car (and you should) then inching up is a habit that’s easy to drop and has absolutely no downsides whatsoever. We promise that those centimeters aren’t going to amount to much more than a particularly wide step in the end.

No Need for Neutral

Though manual drivers may be used to throwing their transmission into neutral when they’re stopped at a light, there’s no reason to do so in a DCT equipped vehicle. The transmission will force the clutch to disengage when it feels the brake pedal being applied.

Brake on the Inclines

If you’re used to driving an automatic, then you’ve probably been stopped on an incline in the past, with nothing but your torque converter holding you in place. And torque converters can handle that, but DCTs will incur some wear and tear from this because asking clutch discs to hold a car in place is really a lot to ask from the clutch of your vehicle if you want it to live a long and healthy life. Use your brakes so that they’re taking the strain rather than the clutch. This is for parking as well, when you really should engage your parking brake so that it can be what holds your vehicle in place.

DCT: Not a Manual, Not an Automatic

Sure, a DCT isn’t a true manual, and many purists will argue that you lose the feel of changing your own gears. But you’ll notice those same purists aren’t in a hurry to pull the synchros out of their transmission and try to pull off shifts without some assistance. The truth is that very few of us have lived in an era where shifts were totally unassisted. How you use that assistance is also a valuable skill, and unlike a continually variable transmission, a DCT has true gears that are shifted and give you the feeling of driving a manual. With paddle shifters, the only thing you’re really missing out on is the cool factor associated with grabbing your shifter and flinging it around like a Fast and the Furious extra. The DCT can pull off gear shifts faster than a human foot will ever be capable of, and if you know what you’re doing, they can also be a lot of fun.

Sources: Engineering Explained | Gear Patrol | Image Credit: Car and Driver | Gear Patrol | Ford | Tremec

Advantages and Disadvantages of Dual Clutch Transmissions

Dual-clutch transmissions are one style of manu-matic transmission that have been growing in popularity. Now, the Shelby GT500 is getting a dual-clutch transmission, leaving many enthusiasts wondering how these transmissions differ from traditional automatic transmissions, and how to drive them. Though dual-clutch transmissions aren't exactly automatics, they differ from manuals in several key ways, and modifying your driving habits can increase the life of your clutch.