ILMA Compoundings July 2018 - 37

One other type of automatic transmission that has created
interest has been the dual-clutch transmission (DCT). It
features two separate clutches and two separate gear-sets that
are typically contained within one transmission housing.
The DCT actually operates like two manual transmissions
with one system operating odd gears (i.e., 1-3-5-7) while the
other system operates the even gears (i.e., 2-4-6). The dual
transmissions of the DCT are designed to work as one unit
providing smooth shifting when operating in the automatic
mode. Some DCT designs provide flexibility to the driver by
offering a manual shift control while the DCT functions in a
semi-automatic mode. This is one reason for the popularity of
the DCT in Europe, where manual transmissions have long
been an important offering to the automotive industry.
The DCT has a strong European influence and is a popular choice in both Eastern and Western Europe. Asia-Pacific,
particularly China, is another important market for DCTs,
where fuel economy benefits of up to 5 percent can be
observed when compared with conventional step-type
transmissions.
A summary of automatic transmission installations for
2015, with estimates for 2020, are provided in Figure 3.
Information from IHS Markit suggests a continued growth
in the DCT segment from 2015 to 2020, with Europe and
China remaining key growth markets. IHS Markit suggests
that DCT transmissions could represent as much as 20 percent of the new automatic transmission installations by 2020,
but growth in North America is expected to be much smaller.
In fact, industry forecasts suggest that DCT transmissions
should only represent between 5 and 6 percent of the total
North American transmission market by 2024 (see Table 2).
However, this would represent a higher than normal growth
rate for North America of approximately 7.5 percent between
2016 and 2024.
DCTs are the fastest-shifting road car transmission available. They are known to shift faster than what a professional

Table 2
North American Transmission Trends
Share %
Transmission Type

2006

2016

2024

Manual

7.4

6.0

4.5

Automatic

89.3

72.0

65.3

CVT

3.2

18.6

24.0

DCT

0.1

3.4

6.2

Total

100.0

Source: AutoForecast Solutions

racing driver can achieve using a manual transmission.
DCTs can also shift faster than cars equipped with singleclutch automated-manual transmissions (AMTs), also
known as single-clutch semi-automatics. With smooth
shifting capabilities, the DCT is an excellent selection for
many conventional road cars.
The first series production road car with a DCT was the
2003 Volkswagen (VW) Golf Mk4 R32. Today, VW (which
includes VW, Audi, SEAT and Skoda) represents the largest
user of DCTs, with Getrag (which sells to many OEMs),
Daimler and Honda as other key users.
DCTs are offered in either a dry or wet clutch mode.
The dry clutch DCT is normally associated with smaller
engine designs with lower torque levels. Higher torque
applications use the wet clutch design on which the clutch
and gear components are lubricated from a single sump. An
alternative option for the wet clutch DCT is a dual sump
system in which the gear and clutch operate from dedicated
sumps. The use of dry and wet sump DCTs is fairly evenly
split today. Future growth is expected to favor the wet sump
DCT design.
The lubricant requirement for a dry clutch DCT is
typically a manual transmission fluid (MTF). Wet clutch
transmissions, however, are more complicated since the
lubricant must provide both gear protection (consistent
with an MTF) and clutch friction control as normally
observed with an ATF (automatic transmission fluid).
Additional requirements for a wet clutch DCT fluid include
anti-shudder friction durability, shear stability, control of oil
oxidation, seal protection and excellent viscometric properties under both high and low temperatures.
Since these transmission systems are challenging and
unique to lubricate, specially designed fluids will be
required. This will create additional complexity to the North
American ATF market since the industry remains quite
fragmented with both licensed and unlicensed product
offerings. Nearly 50 percent of the current North American
ATF market demand is for unlicensed fluids with performance claims against older GM and Ford specifications.
These can be formulated with conventional Group II or, in
some instances, even Group I base stocks. The remainder
of the North American market represents specialty fluids
with formal OEM approvals. This includes multivehicle
transmission fluids for which higher quality Group II+
and Group III base stocks are normally used. It is the latter
higher-performance market in which DCT-approved fluids
will ultimately reside.
Henderson is president of K&E Petroleum Consulting.

ILMA Compoundings July 2018

Table of Contents for the Digital Edition of ILMA Compoundings July 2018