Automatically First
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1 Introduction to Automatic Transmissions 7 Why do we need a transmission? Why do transmissions need dedicated lubricants? How do Automatic Transmissions work? Types of Automatic Transmission
2 Automatic Transmissions Explained
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How do Step-type Automatic Transmissions work? How do Double Clutch Transmissions work? How do Continuously Variable Transmissions work? How do Toroidal (Traction Drive) Transmissions work? Hybrid Transmissions How do Automated Manual Transmissions work? Advantages of Automatic Transmission Types How does Power Assisted Steering work? Comparing Automatic Transmission types
3 Market Trends
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The market in numbers Fascinating facts The European additive service fill market Key trends
Contents
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4 Afton® ATF Range What do additives do? Additives – which, what and how? Afton ATF range summary Product benefits Fuelling efficiency Testing targets Afton® ATF service fill approvals Viscosity classification for ATFs Typical ATF formulations
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5 Specifications ATF specifications – GM ATF specifications – Ford Service fill specifications – Europe Service fill specifications – North America ATF tests explained
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6 Appendix Driveline dictionary Acronyms answered Base stocks explained Base stock comparisons
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Automatically First
Introduction
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Contents
Universal (STOU)
Transmission & Hydraulics (UTTO)
Mining & Construction (TO-4)
The Afton® Driveline range of lubricant additives covers Automatic Transmission, Automotive Gear and Off Road applications. This book focuses on Automatic Transmissions: the different types of transmissions; market trends in hardware and fluids; as well as the additives and specifications for Automatic Transmission Fluids.
Off Road
It is designed for our oil company partners, our distributors, the OEMs and our internal staff. Indeed it’s for anyone who wants to find out why Afton Chemical is Automatically First™.
Step-type Automatic Transmissions
5
Introduction
Driveline Automatic Transmission Fluids
Continuously Variable Transmissions
Double Clutch Transmissions
Automotive Gear Oils
Power Steering
Manual Transmissions
Axles
Automatically First
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Introduction
Introduction to Automatic Transmissions
Automatically First
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Why do we need a transmission? Vehicles need transmissions to:
Friction – which needs to be optimised to satisfy specific requirements of friction elements such as synchronisers, clutch linings and brake bands
Transfer power from the engine to the driveshaft and the differential, in order to rotate the wheels
Friction retention and resistance against oxidation under extreme thermal conditions
Vary the torque, speed and direction by changing the gear ratios
Shear stability – to withstand rigorous shearing in gears and pumps
Enable the car to pull-away from standing / launch, requiring high torque
Air release and foam control
Allow the engine to operate at its optimum efficiency where fuel consumption is minimised
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Apart from basic functions such as lubrication, gear protection and cooling, many extra properties are required:
Whether a Manual, Semi or Automatic Transmission, all power flows in via the engine output shaft. The gear ratios available then enable the transmission output shaft to be spun in differing proportions to the engine speed. The transmission output shaft delivers torque to the final drive, where it splits outwards via a differential to rotate the wheels
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Introduction to Automatic Transmissions
Cold flow properties – for easy gear change and hydraulic functioning at low temperatures
Why do transmissions need dedicated lubricants?
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Introduction to Automatic Transmissions
Automatic Transmissions can be distinguished from Manuals by their ability to change from one gear ratio to another automatically as the vehicle moves. In a Manual Transmission, when the clutch is activated to change gear, the engine is completely disengaged from the transmission and therefore drive to the wheels is temporarily lost. In an Automatic Transmission, gear changes are achieved in such a way that there is minimal loss of torque flow through the transmission.
10 With Automated Manuals, despite varying levels of control over areas such as clutch activation and gear selection, a loss of drive during gear shifting (however brief) is still a common characteristic. Today there is an increasing variety of transmission designs. The choice of transmission type will depend on the vehicle design, vehicle class, engine position and engine power.
How do they work?
Rear wheel drive cars
Front wheel drive cars
Transaxle (transmission integrated with final drive)
Engine (mounted transversely)
Transmission (mounted longitudinally)
Drive Axle with Differential
Engine (mounted longitudinally)
Driveshaft
Automatic Transmissions Explained
Automatically First
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Power flows from the engine into the torque converter and on through the planetary gear sets of the transmission, before heading out to the driven wheels. The gear ratio selected by the transmission itself depends on sensors measuring parameters such as wheel speed, engine rpm, load and throttle position. Based on this feedback, a computer activates the hydraulic system controlling the clutch packs and bands, selectively freeing up or holding different elements of the planetary gear set to provide the optimum gear ratio. This computer control can be manually over-ridden in some Step-type ATs, allowing the driver to select the gears using a gearshift. However the computer maintains overall control and will not permit gear changes that could damage transmission components or the engine. As oil passages in the transmission are narrow and the clearances are tight, ATF cleanliness (oxidative stability, dispersancy) is essential. The presence of air would be detrimental to hydraulic operation as is water or any foreign material.
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Automatic Transmissions Explained
Automatically First ™
How do Continuously Variable Transmissions work?
Low Gear
DriveCone Pulley
Drive or Primary Pulley
Push Belt
Power flows from the engine through the input shaft to the primary pulley, via the belt or chain to the secondary pulley, and out to the final drive. With an infinite number of extremely close gear ratios and no loss of drive during gear transitions, the engine can operate in its most efficient rpm range at all times. This maximises fuel economy and minimises engine emissions. Belt and chain CVTs require a starting device. Modern versions tend to rely on electronically controlled wet clutches or torque converters, the latter having some negative impact on fuel economy. Some drivers find the continuous power delivery provided by a CVT unsettling, expecting instead to feel clearly defined gear changes. In some CVTs the gear ratio can be preset (i.e. manual mode) but this reduces the transmission efficiency. There are no gears to create gear ratios in a CVT. Instead the design typically involves two pairs of
cones mounted on shafts. Each cone pair acts like a pulley: when the cones move together they create a larger diameter pulley and, when moved apart, a smaller one. Because the pulleys can (within geometrical limits) be any diameter in relation to each other, the number of ratios available is effectively infinite. The two pulleys must be connected. Drive ThisPulley is traditionally done with a push belt or a pulling chain. Originally using dry running rubberised materials of limited life, belts and chains are now generally made from steel and lubricated with transmission fluid. The level of steel to steel friction between belt / chain and pulleys has to meet the constantly changing torque transfer requirements including a safety margin. To avoid slippage, which would cause extensive wear or even breakage, Driven Pulley a torque sensor controls the clamping pressure and thus the tension of the belt or chain.
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Drivenor Pulley Driven Secondary Pulley
Automatic Transmissions Explained
DrivePulley or Primary Pulley Drive
Push Belt
High Gear
Cone
Driven Pulley
Driven or Secondary Pulley
Market Trends
Automatically First
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Afton® ATF Range
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Afton ATF Range ®
What do additives do?
In automotive applications, base oils are not sufficient to meet today’s lubrication requirements, either because they are not able to perform satisfactorily or to perform for long enough. Additives are designed to improve the inherent properties of the base oil, either by: modifying the oil protecting the oil protecting the hardware ATFs are characterised by their frictional performance which can generally be evaluated in terms of shift-feel characteristics, torque capacity and friction durability.
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ATFs are specifically formulated to ensure that the fluid friction characteristics provide optimum transmission of torque through the torque converter and allow correct
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Afton® ATF Range
functioning of clutches, and bands where fitted. ATFs also function as a heat transfer medium as well as fulfilling basic lubricant requirements such as, corrosion protection; foam control, wear control, thermal and oxidative stability and material (elastomer, plastics, adhesives) compatibility. Most, but not all, service fill ATFs are dyed red to distinguish them from other automotive lubricants to prevent misapplication. ATFs generally have exceptionally good low temperature properties to allow the transmission to function in extremes of temperature. Because of their all round performance, ATFs are often used as lubricants in areas other than Automatic Transmissions, examples include, power steering, hydraulic and air compressor applications.
Automatic Transmissions Specific Needs Specific friction characteristics for: Correct operation of torque converter and clutches Optimum torque transfer to the transmission Friction durability Common Needs Cooling / Heat dispersion Load carrying Anti-oxidation / thermal stability Anti-corrosion / rust inhibition Anti-foaming Shear resistance Suspend dirt Efficiency / fuel economy Bearing and seals protection Long lifetime Pitting protection Specific Needs Synchroniser performance Load carrying (gears) Friction durability
Double Clutch Transmissions
What makes Afton ATFs Automatically First? ®
ATFs are generally considered to be amongst the most complex and sophisticated of all lubricants. The additives are formulated using a delicate balance of componentry, and must be capable of functioning well in a variety of transmission, engine and vehicle combinations. Afton Chemical is the global leader in additives for ATFs – the culmination of many years’ research and development in collaboration with the world’s leading OEMs. Afton leads the way in additives for traditional step-type automatics and newer technologies such as DCT and CVT.
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After many years formulating additive technologies for ATFs, Afton has the process of meeting the specific requirements of individual OEMs down to an art. Typically a core additive is chosen with a basic level of lubrication performance in terms of anti-wear and scuffing protection. Afton then utilises its
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Afton® ATF Range
vast database and extensive testing facilities to model fluid friction performance in the OEM defined hardware. The Afton model takes account of fluid performance in the different transmission elements, e.g. torque converter, shifting and start-up clutches and predicts the performance of this hardware under specific operating conditions such as pressure, temperature and rotational speeds. This statistical modelling process gives Afton the capability to offer OEMs ‘friction on demand’: the ability to define an ATF which exactly matches their requirements and provides optimum transmission performance. The ultimate challenge though is to maintain excellent fluid friction performance in the field over the application lifetime. Afton ATF technology can give OEMs the capability to extend transmission oil drain intervals to well beyond 150,000km, even in the most severe
applications. Afton’s additive technology gives the OEM the security of knowing that the friction and torque capacity performance of their ATFs is maintained during the designed lifetime of the transmission. Afton remains committed to further advancing ATF technology, for example by working with our OEM partners to develop advanced lowviscosity ATFs with proven fuel economy benefits. So in terms of advanced ATFs, Afton is Automatically First™.
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Afton® ATF Range
Typical ATF formulations based on HiTEC® 2414 TEST
TASA GM GM GM IID IIIG IIIH
HiTEC® 2414, % wt. Nexbase 3043, % wt. HiTEC® 5710A, % wt.
5.9
11.9
11.9 25.0
11.9 35.0
2.0
The use of one additive for a number of applications as shown ExMo 100SN, % wt. 92.1 88.1 63.1 53.1 here can give cost, logistical and inventory benefits. 2
Kinematic Viscosity at 100ºC, mm /s 7.3 7.6 7.5 7.5 Kinematic Viscosity at 40ºC, mm2/s 35.1 37.8 36.8 36.2 Viscosity Index 178 169 173 176 25,600 28,000 18,900 18,200 Brookfield Viscosity at -40ºC, mPa.s Kinematic Viscosity at 100ºC after 5.5 5.6 5.5 20 hour KRL shear, mm2/s
HiTEC® 2414 The world’s most versatile ATF additive HiTEC® 2414 uniquely offers a range of different performance levels from TASA to GM IIIH. With good base stock compatibility, this versatility allows stock inventories to be reduced and logistical benefits to be gained. A market leading solution from the market leader in ATF technology.
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Specifications
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Specifications
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ATF tests explained Anti-shudder durability
Anti-shudder durability tests evaluate the anti-shudder performance of an ATF, e.g. in shifting or torque converter clutches, as the fluid is aged over time. Durability tests are often run under conditions where the clutch is allowed to ‘slip’ i.e. is not fully closed, during testing. Antishudder durability can be measured using various friction test rigs including, the SAE No.2, Low Velocity Friction Apparatus or the ZF built ‘GK rig’. Each test will measure fluid friction on ageing under specific test conditions to give an assessment of fluid performance. Band friction test
Band friction tests determine the brake band friction characteristics of an ATF. A band and drum are assembled in an SAE No.2 machine and a test sequence is run where the drum is first rotated and then stopped by applying pressure on the band. This cycle is repeated
over 150 hours of operation (DEXRON®-VI) with friction measurements being taken during the stop cycle. Torque capacity and stop times must remain within specified limits for the test duration. The end-of-test parts are rated and compared to those tested using an approved reference oil.
Bearing testing
Bearing testing, such as the FE8 Bearing Test is used to examine the properties of lubricants running in bearings under specific operating conditions and specifically wear protection. With oil lubrication testing, oil is fed to the bearings via a pump and is allowed to flow back to the tank via a drain hole for recirculation back around the circuit and over the bearings again. The operator can vary several factors in this test including speed, temperature, test duration and axial test load applied to the bearing. Typically a test will run for a fixed duration at which point the condition of the bearing including weight loss will be measured against OEM set criteria. Clutch plate friction test
Plate friction tests are used to determine the friction characteristics of an ATF in clutch applications. Plate friction tests, e.g. for GM are typically run on an SAE No.2 machine using
Appendix
Automatically First
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Driveline dictionary Clutch pack
A set of alternating clutch discs and plates that can be hydraulically opened or closed thus releasing or holding components of a transmission.
Continuously Variable Transmission (CVT)
A gearing system that uses a continuous range of ratios, as opposed to discrete step changes.
Converter clutch (CSTCC or ECCC)
A clutch that can be used to partially (slipping mode) or fully lock the pump and turbine halves of the torque converter, thereby recovering efficiency losses.
D ifferential
A device that allows vehicle wheels to rotate at different speeds, e.g. when cornering.
Double Clutch Transmission (DCT)
A type of Automated Manual Transmission that uses two clutch systems working in tandem. Also referred to as Dual Clutch.
A strap mounted around the outside of a clutch pack drum that when activated, stops the drum from rotating.
Driveshaft
A device that transfers power (or drive).
Dry clutch
A type of clutch where the components are not immersed in a lubricant.
C entrifugal force
A force that is exerted away from the axis when a body is in rotation.
E ngine crankshaft
The part of the engine that converts the linear motion of the pistons into rotational motion.
Clutch
A mechanism for transmitting rotational force, that can be engaged and disengaged.
Epicyclic system
A gear system where the rotational axes of the gear(s) move, e.g. the planets in a planetary gear set.
A dditive
Any material added to a base stock to change its properties, characteristics or performance.
Automated Manual Transmission (AMT)
A Manual Transmission where gear changes are controlled by hydraulic / electronic rather than mechanical means.
Automatic Transmission (AT)
A transmission system that can change between gear ratios automatically as the vehicle moves.
Automatic Transmission Fluid (ATF)
A lubricant used in Automatic Transmission systems.
Automotive gear
An array of toothed wheels used to transfer power and to change the ratio of torque to rotational speed, or change rotational direction.
B ase stock
The base fluid, usually a refined petroleum fraction or a selected synthetic material, into which additives are blended to produce finished lubricants.
Brake band
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Appendix
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Appendix
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Noise, vibration and harshnes
OEM
Original Equipment Manufacturer
PAO PAS PIO PPD
Poly Alpha Olefin Power Assisted Steering Poly Internal Olefin Pour Point Depressant
RPM
Revolutions Per Minute
SAE SF STOU
Society of Automotive Engineers Service Fill Super Tractor Oil Universal
TAN TASA TBN
Total Acid Number Type ‘A’ Suffix ‘A’ (GM Specification) Total Base Number
UTTO
Universal Tractor Transmission Oil
VDT VI VII VM
Van Doorne Transmissie Viscosity Index Viscosity Index Improver Viscosity Modifier
ZF
ZF Friedrichshafen
Aluminum Beaker Oxidation Test Automated Manual Transmission American Society for Testing and Materials Automatic Transmission Automatic Transmission Fluid
C-4 CSTCC CVT
Allison Transmission Specification Controlled Slip Torque Converter Clutch Continuously Variable Transmission
DCT
Double Clutch Transmission
ECCC E-H E-M EP
Electronically Controlled Convertor Clutch Electro-Hydraulic Electro-Mechanic Extreme Pressure
FE FF FWD FZG
Fuel Economy or Fuel Efficiency Factory Fill Front Wheel Drive Forschungsstelle für Zahnräder und Getriebebau
GM GTL
General Motors Gas To Liquid
IC ICE IR IVT
Internal Combustion (engine) Internal Combustion Engine Infra-Red Infinitely Variable Transmission
JASO
Japanese Automobile Standards Organization
Common Units
KV
Kinematic Viscosity
mPa.s mm2/s
MB MT MAN
Mercedes-Benz Manual Transmission Maschinenfabriken Augsburg Nuernberg
Unit for dynamic viscosity, also expressed as centipoise (cP) Unit for kinematic viscosity, also expressed as centistokes (cSt) Kinematic viscosity = Dynamic viscosity / density (g/cm3)
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NVH
ABOT AMT ASTM AT ATF
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Acronyms answered
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