With electric drivetrains dominating the current automotive news, it is easy to overlook the variety of transmissions available for today’s automobiles. With over 95 million globally-produced motor vehicles, demand for personal transportation is still growing with population, despite a 1.7% decline from 2017-2018. This high demand is driving dynamic change in manufacturer strategies, as OEMs balance popular ICE options with the disruptive innovation driven by the market.
In this article, we'll take a brief look at some of the most popular types of transmissions in use today.
Ford Toploader transmission.
Manual (or standard) transmissions operate by leveraging a variable gear ratio for a given driving condition, balancing torque, speed, and power at the driver’s discretion. While an option in about 1 out of 5 new vehicles, manual transmissions comprise less than 3% of US car sales, though they remain present in many existing vehicles. Manual transmissions were historically more fuel-efficient than their automatic counterparts, though current automatic transmissions now exhibit improved fuel economy over manual ones.
Once automatics cleared that hurdle, coupled with decreasing consumer interest in the technology, demand for manual transmissions dropped sharply. Automakers welcome this shift, since removing manual transmission from their portfolios improves profitability by reducing a significant design option. Though automatic transmissions are the overwhelming consumer choice, there are several variations within that space.
Advancement in manufacturing techniques is a factor that may perpetuate the viability of manual transmissions for its loyal consumer base. Due to having fewer and less complex components than automatic systems, manual gearboxes could leverage improved manufacturing methods that could help decrease their production costs.
GM, Ford, Honda, Hyundai, Kia, Nissan, Subaru, and Toyota are among the manufacturers still offering multiple options of standard transmissions.
Hydraulic Planetary Automatic
8-speed ZF 8HP transmission, showing the torque converter, gearsets, clutch plates, and hydraulic and electronic controls. Image courtesy of Stefan Krouse
The most common type of automatic transmission uses locking and unlocking planetary gears when [automatically] shifting, and it uses a hydraulic coupling to transmit rotational power instead of the manual’s clutch. A defined number of gear ratios comprise the engine speeds, and the passengers still may feel the gears shifting as a result. The move to electric drivetrains decreases the need for multiple speeds, though the Porsche Taycan offers a 2-speed automatic for increased performance.
DCTs are an advanced technology that originated in Germany. These automatic transmissions employ two independent gear set and clutch circuits. Speeds alternate between the rods so that the even-numbered gears are on one rod and the odds are on another. The reason for this is so that the controls can preset the next gear while the vehicle operates in an adjacent one. When the car needs to shift, the computer releases the current-speed clutch and engages the other.
The dual-clutch transmission is an intermediate step between the distinct gear positions of the hydraulic planetary automatics and infinite-speed models (discussed below). Volkswagen, Nissan, Ferrari, and McLaren are leaders in DCT technology, which is also present in the Porsche 911. Porsche terms its DCT the “PDK,” an acronym for the German translation of double-clutch transmission.
Continuously Variable (CVT)
Toyota Super CVT-i
As opposed to the hydraulic planetary transmission’s multiple-speeds, the CVT is single-speed and transitions the vehicle through a continuum of gear ratios. The most significant benefit of this transmission style is the ability to smoothly transition to operating points that maximize the engine’s efficiency. This benefit is in contrast with hydraulic planetary transmissions, which may have a peak efficiency between two gear ratios for a given output speed.
Honda, Nissan, and Toyota offer the most vehicles with CVT transmissions. This fact is not surprising, since one of the largest global suppliers of CVT transmissions, Nissan subsidiary JATCO, is the product of a merger between Nissan and Mitsubishi transmission divisions. Honda manufacturers its CVTs, and Toyota uses its own subsidiary Aisin to manufacture the transmissions. As a result, Japan dominates the market on this technology.
The automotive industry is infamously competitive, and each market player is searching for an advantage to ensure its long-term viability at the advent of the EV revolution. Electric cars are likely to disrupt the industry in the coming decade, and OEMs must prepare for the possible transition of the ICE from a market-dominant growth technology to a legacy niche. Advanced manufacturing techniques and product innovations are two ways car manufacturers maintain profitability during this market shift.
Spiral bevel gears use helical teeth to reduce noise and vibration fatigue. A modified tooling package forms the shape of the helical teeth, and improved durability performance decreases the transmission cost
Reduction of manual transmissions helps to reduce the component count for OEMs, though the depreciation impact of the capital transfers to existing equipment
Additive manufacturing, though not yet suited for huge volumes or large component sizes, offers the material reduction of light-weighted metal with the joint/feature inclusion of castings. Ford and BMW are partnering with 3D printing manufacturers to adapt their vehicles to the increased connectivity, and infotainment consumers expect from new vehicle models.
Improved automation works in concert with the expanding amount of smart technology within the manufacturing facility. The robots can record and analyze large amounts of data to self-optimize as they are running, allowing engineers to realize instant, real-time process improvements without the shutting down to reprogram.
Electric vehicles and the IoT are disrupting the automotive industry like never before. To address the changes, the product and process development of transmission components allow the driver a better experience, with improved efficiency and higher vehicle durability. Innovation and overall drivability are still critical metrics for OEMs, who know that the automatic-transmission ICE will be in-demand for years to come.