Gear and transmission lubricants

Citation

(1998), "Gear and transmission lubricants", Industrial Lubrication and Tribology, Vol. 50 No. 1. https://doi.org/10.1108/ilt.1998.01850aad.001

Gear and transmission lubricants

Gear and transmission lubricants

The demands on gear lubricants have increased steadily as gear tooth loadings have been raised, gearbox sizes have been reduced with adverse effects on running temperatures, operating periods have been extended and maintenance reduced. Manufacturers now offer a wider range of oils than ever before. While lower priced mineral oil based oils and semi-fluid greases are still the most widely used, synthetic and part-synthetic products often give the best results, and account for about 10 per cent of the market. The composition of a typical industrial gear lubricant range is shown in Table I.

Automotive driveline fluids

The development of automotive gearbox and axle lubricants has been more rapid than that of industrial gear oils. This has been necessitated by the continuing demand for improved performance, better durability, improved fuel economy and reduced emissions and by the heightened customer expectation of ease and smoothness of operation.

There are three basic categories of fluid involved: automatic transmission fluid (ATF); manual gearbox oils; and final drive lubricants.

ATF

A primary role of the ATF is to transfer torque from the input impeller of the torque converter via the stator to the turbine which is connected to the gears. The fluid then has to lubricate and cool the friction surfaces, lubricate the gears and bearings, act as a hydraulic fluid, prevent the formation of deposits and inhibit corrosion. Over 85 per cent of the cars in the USA are conventional automatics requiring ATF compared to less than 10 per cent in Europe. However, the figure rises to over 80 per cent of European cars with an engine capacity of over 3 litres. The two dominant passenger car ATF specifications are Dexron 11E and 111 from General Motors and Ford's Mercon fluid. Most other manufacturers will accept either as service-fill in their transmissions. Ford used to require significantly different frictional characteristics for its "harder" fluid but now the differences are only marginal. The ATF formulations include up to 11 different additives, including oxidation inhibitors, metal deactivators, corrosion and rust inhibitors, anti-wear agents, viscosity modifiers to reduce thinning at elevated temperatures, dispersants to prevent the formation of deposits, friction modifiers such as sulphonates and seal swell agents.

Conventional automatic transmissions are now being seriously challenged by continuously variable transmissions (CVT). The latest automatic Nissan models in Japan are being offered with CVT transmissions only for engine sizes up to 2.0 litres. CVTs require substantially different lubricant characteristics from those of an ATF. Special lubricants are being developed for both the push belt expanding pulley and the toroidal variator types of CVT.

Manual gearbox oils

Manual gearboxes have straight spur or helical gears and synchromesh cones (Plate 1) which require oils with only moderate EP properties. This can be provided by the zinc dialkyl dithiophosphate (ZDDP) in the engine oil. Too much additive can adversely affect the synchromesh action. ATF is increasingly being specified for precision manual gearboxes to give better shift quality at low temperatures. Multi-grade SAE 75W-90 or 75W-140 are also coming into favour where their higher cost is acceptable.

Final drive oils

Final drive spiral bevel and hypoid gear lubricant formulations have changed over the past 60 years from the early oils containing lead soaps and dissolved sulphur to "universal" gear oils with combinations of ZDDP and chlorine/phosphorus/sulphur compounds. As increased performance was demanded these were succeeded in their turn by today's sulphur/phosphorus additives based on sulphurised olefins and phosphorus esters. Triazole and thiadiazole nitrogen containing additives can be present in addition as corrosion inhibitors and to give additional anti-wear protection.

General

Automotive driveline oils are required to operate at increasingly higher temperatures for a variety of reasons.

Lower bonnet lines mean poorer under-bonnet air circulation. Higher gear tooth loads mean smaller gearsets for the same torque transmission, reduced gearcase capacities mean less oil to dissipate the heat generated. With front wheel drive cars the gearbox is also affected by heat soak from the engine. Manufacturers are now wanting manual gearbox oils to operate at up to 160°C compared to the historical requirement of 140 to 150°C. Oxidation test temperatures for ATFs have risen to 170°C from the 150 to 160°C levels of the 1980s. At the same time "fill for life" maintenance-free operation is being demanded by passenger car drivers, where life is 250,000km.

Plate 1 Five speed gearbox for the Mini ­ from Jack Knight Developments. First and reverse gears are spur gears. Gears 2 to 5 are helical gears

Specifications

The US Army Ordinance Department began specifying or "qualifying" gear lubricants in 1943, starting with MIL-2-105. In 1977 it passed this process over to the Society of Automotive Engineers (SAE). Performance classification tests have been developed in the USA by the Co-ordinating Research Council (CRC) and the American Society for Testing and Materials (ASTM). The American Petroleum Institute (API) assigned performance designations from GL-1 (oil with no performance additives) to GL-5 (oils for hypoid gears at high speed and/or low speeds and high torque), the latter equivalent to Mil-L-2105D. GL-6 (oil for gears with very high pinion offset) is now obsolete. Basic automotive gear oil specifications in both Europe and the USA are the API GL-4 for manual gearboxes and GL-5 for final drive axles. A new heavy duty manual transmission specification, API MT-1, has been introduced to overcome problems of deposit formation and seal compatibility. It also includes new tests for synchroniser and anti-wear performance and an FZG gear wear test.

The US military specification MIL-PRF-2105E has been updated to include API MT-1.

PG-2 is a new ASTM upgrade of the GL-5 axle lubricant specification designed as a higher performance hypoid lubricant. It will probably include all the current API GL-5 tests, a spalling test, thermal stability, cleanliness requirement and seal compatibility tests.

The SAE axle and manual transmission lubricant viscosity classifications used almost universally are shown in Table II.

Multigrade gear oils meet the low temperature viscosity limit while at the same time exceeding the minimum viscosity at 100°C. For example, an 80W-140 oil would have a viscosity of 150,000 cP at less than ­26° and a viscosity of greater than 24cSt at 100°C. Its viscosity at 40°C would be about 220 cSt.

The approximately equivalent ISO viscosity grades at 40°C of the SAE classes are: 70W and 75W (22 to 46); 80W (46 to 100); 85W (100 to 150); 90 (150 to 320); 140 (320 to 680); and 250 (680 to 1,500).

CEC transmission lubricant tests

The Co-ordinating European Council for the Development of Performance Tests for Transportation Fuels, Lubricants and other Fluids (referred to as the CEC), has approved or is developing a number of tests for gear and transmission lubricants.

The CEC continues to monitor the two approved tests, CEC L-07-A-95 "Load carrying capacity test for transmission lubricants ­ FZG gear machine" and CE L-48-A-95 "Oxidation stability of lubricating oils used in automotive transmissions by artificial ageing". Oxidation stability is tested by bubbling air through oil at temperatures dictated by the temperature of the actual application; there are two versions of the test, one developed by the DKA (the German national organisation in the CEC) and the other by the GFC (the French national organisation in the CEC). Which method to use depends on the end application of the oil. Measurements are made of viscosity, total acid number (TAN), insolubles and by infra-red spectra.

There are two tentatively approved tests for which approved status was to be sought in 1997. They are CEC L-11-T-96 "Automatic transmission fluid (ATF) friction test apparatus" and CEC L-45-T-93 "Viscosity shear stability of transmission lubricants using a taper roller bearing test rig". The two versions of the DKA's ATF friction test rig, 1A and 1B, both designed by ZF Passau, allow assessment of the shift quality of automatic transmissions with the fluid on test by measuring the frictional characteristics of the clutches. These in turn are influenced by the friction material and the transmission oil. The third tentative test is the CEC L-66-T-92 "Synchromesh gearbox lubricants test using the Hurth SP 180 synchromesh test rig". The aim of the tests is to develop a procedure for studying synchromesh endurance and friction and wear performance using synchroniser elements from passenger car and commercial vehicle gearboxes with different friction materials and lubricants.

The CEC created in 1992 an investigation group IT-067 to select and develop a well defined gear surface pitting test method which would be discriminating between representative lubricants and would give reproducible results in agreement with field experience. Test results on the FZG rig with three different types of gear showed that there could be a factor of up to three between "good" and "bad" pitting oils. There were two papers on this work from the Technical University Munich at the 1997 CEC Symposium. Round robin tests using two reference oils, four tests per oil and all gears from the same batch were run last year involving ten laboratories.

An investigation group IT-075 was set up in 1996 to examine the need for and, if necessary, propose a test method for evaluating the fuel economy impact of transmission oils. A recent paper from the Rover Group described transmission losses as either parasitic or power proportional. Both types could be reduced by the choice of lubricant to improve the fuel economy of the vehicle.

Drain intervals

Also at the CEC Symposium there were papers from additive manufacturers showing that extended drain periods of up to 400,000km could be obtained even with mineral oil based axle and transmission lubricants. Until recently most heavy duty trucks in North America operated with a 160,000km drain interval for their axles. In Europe the axle drain interval for commercial vehicles was typically 90,000km.

Longer drain intervals are attractive provided that the lubricant can provide adequate protection over the extended period. Some of the performance areas included in the latest axle oil specifications, such as the Mack GO-J, API MT-1 and API PG-2 were listed as ­ thermal stability, deposit formation, oxidative stability, elastomer compatibility, non-ferrous metal corrosion protection and surface fatigue (spalling).

Continuously (CVT) and infinitely (IVT) variable transmissions

The expanding pulley CVT was successfully developed for commercial use by the Dutch industrialist Dr van Doorne after World War II. Known as the Variomatic it was used in DAF cars in the 1950s and 1960s in the form of a rubber V-belt connecting two split conical pulleys whose effective diameters could be varied to give different drive ratios by altering the distance between the two halves of each pulley. This type of transmission is still found in many small modern scooters.

The early production DAF CVTs were operated by pneumatics, had a centrifugal clutch and suffered from short belt lives. In the 1970s the Van Doorne's Transmissie bv engineers came up with a steel belt version from which evolved the present push belt design. Around one million vehicles with engine sizes from 0.6 to 1.8 litres have been fitted with the steel push belt CVT since it was introduced commercially ten years ago. But it was only when fully integrated electronic control systems that enabled engine power and torque to be optimized were incorporated that the full potential of these transmissions for improving fuel economy could be realised (Figure 1). CVT production is predicted to reach one million a year and to account for 40 per cent of all automatic cars by the end of the decade.

Figure 1Continuously variable transmission layout

Van Doorne CVT metal push belts have torque transmission ratings from 80 to 300Nm and maximum operating speeds up to 7,500rpm.

CVT lubrication

Correct lubrication with a suitably blended lubricant is critical for the oil immersed CVT drives. Indeed, one car manufacturer had to suspend production for a time when lubrication problems were experienced in service. Operating temperatures are not excessive, with fluid oxidation usually being measured at 160°C. Boundary lubrication (lubricity) characteristics are critical to enable the steel belt elements to "grip" in the circumferential plane while remaining lubricated to ride freely in and out radially against the conical faces of the pulleys as the drive ratios are changed. The contact geometry of the belt links against the pulleys as the point of contact moves both radially and tangentially is complicated and only recently has an effective bench test been developed by ZF in Germany.

Two workers at Paramins Linden Laboratories reported to the recent Gothenburg CEC symposium on screening tests they had developed for candidate fluids for use in CVT transmissions. Employing readily available test equipment, they designed two tests that used a belt element (Figure 2) and a simulated pulley made of hardened steel with a suitable surface finish. The rigs offer different geometries ­ one with the test pieces parallel to the axis of rotation and the other with the specimen perpendicular. This allows evaluation of the tribological characteristics in different configurations and sliding modes. Lubricant performance is ranked on the basis of overall level of friction, friction stability, and temperature and load dependence of friction.

Figure 2 A CVT push belt would have about 300 of these elements (scale 2.7 times full size)

IVT

IVT toroidal traction drives can be traced back to an 1899 patent and the short lived Hayes transmission fitted to some Austin cars in the 1930s. General Motors in the USA also experimented with double sided full toroidal variators in the 1930s. Forbes Perry of Perbury Engineering developed the concept further in the 1960s. In 1987 Rover Group, for which Mr Perry then worked as a consultant, sold its interest to what is now the British Technology Group and the Torotrak variator was born. The transmission comprises two sets of tilting rollers running between discs with toroidal profile surfaces. It is a true infinitely variable transmission capable of providing all ratios from full reverse to high overdrive. Unlike the Van Doorne CVT it does not need a clutch or torque converter for starting, making for simplicity, reduced weight and lower cost. The properties of the fluid are critical to the success of the drive; in particular a high traction coefficient is needed.

Familiar names such as Santotrac 50 and the naphthenic oil based Sternol Hydratorque are fluids with the necessary high traction coefficients which have been used successfully in industrial applications and in the Harrier constant speed generator drive. However, they have proved unable to cope with the range of operating temperatures and the complex demands made on an automotive transmission fluid. Synthetic lubricants like polyalphaolefins (PAO) are notable for having low traction coefficients and are therefore not suitable.

Shell announced in September 1997 that it had:

developed a new generation of advanced traction fluids to meet the exacting requirements of new, fuel efficient, IVT systems where conventional automatic transmission fluids cannot be used. The availability of effective traction fluids is essential to the success of this revolutionary transmission technology. Shell are using...advanced molecular modelling techniques to design fluids that combine high traction coefficients (the ability to transmit power across a fluid film) with wet clutch performance, gear protection and the viscometric characteristics necessary... Shell's fluids are currently being supplied to a diverse range of prototype applications...including trials being carried out for a number of major vehicle manufacturers who are licensees of Torotrak technology.

CVJ lubricants

Constant velocity joints (CVJ) are the joints in drive shafts which do not impose the cyclic velocity change of the Hooke type universal joint noticeable at larger articulation angles. Constant velocity joints are now used on almost all front wheel drive cars and on many rear wheel drives. These joints take several forms. There are the fixed ball joint or Rzeppa joint, the plunging ball joint with either straight tracks (double offset joints) or crossed tracks (VL joints), all with six balls running in cylindrical grooves. Tripod joints, both fixed and plunging, the latter (GI joint) having needle roller bearings on each of the three-legged inner part, are popular alternative designs of CVJ (Figure 3).

Front wheel drive cars have four CVJs. A fixed joint at each of the front wheels which can be turned through up to 45 degrees for steering and a plunging joint mounted at the gearbox end of each drive shaft. Plunging joints permit axial movement between the inner and outer race of the joint which is needed to allow for the variation in length of the drive shafts as the vehicle suspension moves up and down. As well as two CVJs on each drive half shaft, many rear wheel drive cars have had the Hooke-type universal joints on the propshaft replaced by CVJs to reduce the significant vibration which occurs at angles greater than 3 degrees. Again, one of these would be of the plunging type to accommodate changes in propshaft length. Four wheel drive cars can have as many as 14 CVJs of different types. Figure 3 Some CV-joints shown in part section

GKN, Europe's main supplier of CVJs, categorises greases for CVJs into seven classes depending on the joint type (ball or tripod), the temperature (up to 120 or 150°C), the installed angle and the speed of operation.

The early fixed ball CVJs as found on the Austin Mini from 1959 were first lubricated with standard lithium soap thickened extreme pressure mineral oil grease but soon suffered wear, evidenced by a pronounced clicking sound on going round corners as the balls in the joints oscillated over the worn bearing grooves. The replacement grease was a number 2 modified clay thickened oil containing 20 per cent molybdenum disulphide. In Germany the DKW 11 car of the 1960s had CVJs lubricated with an EP 140 grade oil containing 10 per cent colloidal graphite. Gear oil has generally proved a better lubricant for CVJs but sealing difficulties, ease of assembly and noise and vibration considerations have persuaded most manufacturers to prefer grease. The tripod joints in use in France from the 1960s are lubricated with calcium complex thickened mixed base paraffinic and naphthenic oils. Tripod joints need a lubricant free of solids which could prevent the free movement of the needle rollers. The 1970s saw the use of still popular lithium 12-hydroxystearate thickened greases with 3 per cent molybdenum disulphide and other additives such as polyethylene, lead naphthenate or lead dithiocarbamate. Polyurea thickened mineral oil based greases were first used in 1978. The operating temperature range for current production CVJs is ­40 to +120°C, right at the limit for lithium 12-hydroxystearate and calcium complex soap thickened mineral oil greases.

Today, most base oils used for normal temperature CVJs are naphthenic/paraffinic mixtures although with catalytic dewaxing to improve low temperature performance modern paraffinic base oils can be used as bases on their own. The increasing demands on some joints have meant higher loads, greater installed angles and higher temperatures which can exceed the limits of lithium thickened mineral oil greases. This has meant the use of polymer or complex soap thickened synthetic or semi-synthetic base oils and substantially higher lubricant costs.

Greases have been developed with a polyurea thickener and high temperature anti-oxidants for joints operating at temperatures up to 150°C. A special grease was successfully formulated for Formula 1 car CVJs which experience temperatures up to 200°C. It was polyalphaolefin oil base with a stearate/azelate lithium complex thickener.

Additives

CVJ oils contain numerous additives to improve their physical properties such as tackiness, pour point and viscosity index. Solid lubricant additives include graphite, molybdenum disulphide, polytetrafluoroethylene and polyethylene. While effective in reducing wear, solid lubricants can be centrifuged out of high speed joints and can cause clogging of needle roller bearings. Chemically active additives range from anti-oxidants and corrosion inhibitors to anti-wear, extreme pressure and friction modifying compounds. Friction reducers are particularly valuable in joints operating at large installation angles where the efficiency of the joint can drop below 99 per cent, causing substantial internal heat generation. Lead additives give excellent wear resistance but are being phased out on environmental grounds.

Rubber boots

Various grades of modified polychloroprene have been used as the rubber boot material protecting CVJs since the introduction of the Mini. There is considerable interaction between the rubber and the grease with the plasticiser and protective agents being leached out and replaced by oil from the grease. The base oil then softens and plasticises the rubber but reduces its low temperature performance.

For high temperatures (150°C) silicone rubber is used, requiring that the grease should have a low sulphur base oil and sulphur-free additives.

Shell industrial gear portfolio

Shell Oils has a range of gear oils designed to maintain gears and gearboxes in tip-top condition and to obtain the best possible business returns in terms of time and cost savings.

The main change since the portfolio (see Table III) was launched has been renaming the Hyperia polyalphaolefin (PAO) synthetic oils Omala HD (heavy duty) for the grade with extreme pressure additives and Omala RL (regular loading) for the grade aimed at lubrication applications outside the temperature range of mineral oils.

More details from Shell Oils, Delta House, Wavell Road, Wythenshawe, Manchester. Tel: 0161 499 8500 or Freephone: 0800 414414.

Superior lubricants from Rocol

Five new gear oils and four new compressor oils, have now been added to the Rocol Sapphire range of lubricants. Respectively designed Hi-Torque and Hi-Bar, these advanced oils, asserts Peter Allison, senior production manager who supervised their development, will substantially increase service life while increasing protection against wear, corrosion, fluctuating temperatures and sustained high-loadings.

Both types combine an innovative, finely-tuned blend of additives with a state-of-the-art semi-synthetic base oil. "They are the biggest advance since Rocol started making lubes 120 years ago" is Allison's description ­ who backs his words with details of stringent tests made against all current market-leading brands.

Both gear and compressor oils were subjected to tests for IP 239 Four-Ball weld-load extreme pressure performance, ASTM D892 anti-foaming, and accelerated life by differential scanning calorimetry (DSC). Sapphire Hi-Bar products were also tested for low temperature performance.

Test results

Hi-Torque gear oils: tested against eight comparable oils, the Rocol product reached a 560kg loading during IP 239 extreme-pressure performance tests. The highest rating any other brand reached was 370kg. ASTM D892 tests indicated typical foaming of only 5ml. Others compared had 10 to 130ml. And DSC accelerated life tests showed typical onset of oxidation at 287°C.

Hi-Bar compressor oils: 200kg loading in Four-Ball weld load tests, compared to 140-180kg, zero foaming during ASTM D892 tests (other 80 to 30ml), and 264.5°C for accelerated life tests were achieved. The typical result of low-temperature performance tests was ­30°C for Sapphire Hi-Bar, compared to ­15 to ­12°C for other major brands.

The new Rocol oils have won wide approval: Hi-Torque gear oils are approved by David Brown Radicon, and exceed the standards specified by US Steel 224, AMGA 250.04, and DIN 51517 part 3. Hi-Bar compressor oils meet requirements of DIN 51506 VDL, VC, VCL, VB and VBL classifications.

Distinctive features

The David Brown approved Sapphire Hi-Torque gear oils feature the Rocol start-up protection system (SUPS). This is based on a unique additive with extreme pressure and high load-carrying properties, which shields gear trains from high pressures and extreme temperatures. It is particularly effective at start-up when most wear occurs, and plays a major role in ensuring an extended service life.

Sapphire Hi-Torque oils have excellent compatibility with both mineral and synthetic oils, will not damage seals, and will not affect most types of paint.

Sapphire Hi-Bar compressor oils contain the Rocol L-CO System, which ensures extremely low-oil carry over and enhanced oxidation stability. Again, this distinctive Rocol feature ensures increased service life and extended change intervals, no matter what type of compressor Hi-Bar is lubricating.

Both of the new oils are available in all the commonly-used ISO viscosity grades. They are supplied in 1 litre Top-Up, 5 litre and 25 litre packs, all of which carry detailed labels, and are available immediately from 700 outlets throughout the UK. There is a similar widespread distribution on mainland Europe.

Further product details can be obtained from Peter Allison, Rocol Ltd, Rocol House, Swillington, Leeds LS26 8BS. Tel: 0113 232 2652; Fax: 0113 232 2650.

Plantogear ­ a safe solution for industry

Environmental protection has been a key innovative parameter for Fuchs Lubricants for the last 30 years, long before it became a global issue. Now, after years of sustained investment, Fuchs can boast to be the leader in this field with Planto, a range of rapidly biodegradable lubricants based on natural oils and their esters.

The Plantogear S Series of gear oils forms a central part of this range synthetic based oils which are environmentally acceptable, rapidly biodegradable and have achieved classification in the German Water Pollution Category 0 ­ substances that do not pollute water.

The Plantogear S Series of oils is suitable for all worm, planetary, spur and bevel gearboxes and highly recommended for use in the food, beverage, water and packing industries. They are ideally suited for gearboxes used in protected water areas and gearboxes which could endanger ground and surface waters if leakages occur.

Change-over from mineral based gear lubricants to Plantogear S Series is simple. Plantogear lubricants are fully miscible and compatible with mineral oil based lubricants; however, in the short term, residual quantities of mineral oil may increase the Water Pollution Category to over 0.

Plantogear S products display excellent viscosity/temperature behaviour and thus ensure that an optimum lubricating film is formed regardless of the temperature. These oils have a working temperature range of ­30°C to +90°C and do not attack conventional paint finishes, gaskets or seals. Their ageing stability in the upper working temperature ranges corresponds to that of mineral oils.

Plantogear oils exceed the requirements of DIN 51 517, part 3 for gear oils and DIN 51 524 for hydraulic oils.

For many years Fuchs Lubricants has been reviewing, addressing and pre-empting these new requirements for environmentally aware products world-wide, investing considerably in research and development to ensure that environmental demands are met with products which, in addition, meet both the performance and financial requirements.

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  The Planto range now incorporates:

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  Plantocut S ­ cutting fluids

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  Plantohyd ­ hydraulic oil

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  Plantolube CGLP S ­ slideway oil

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  Plantogel ­ grease

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  Plantogear S ­ gear oil

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  Plantomot ­ engine oil

All Planto products offer the additional benefit of low evaporation and low misting. At the same viscosity, specially selected ester oils evaporate up to 80 per cent less. Workplace pollution caused by oil mist and other machining vapours is therefore significantly lower than with comparable mineral oil based products. To aid worker safety the ester oils used in Planto products are completely free of aromatics, less harmful to the skin and dermatologically superior to mineral oils.

For further information into Fuchs Plantogear or any of the Planto range, please call Cliff Lea, Silkolene Oil Refinery, Belper DE56 1WF. Tel: +44 (0)8701 200400; Fax: +44 (0)1773 823659.

Texaco gear and transmission products

Texaco Lubricants supplies the UK market with a full range of industrial and automotive gear and transmission products.

The industrial products include the Texaco Meropa line of gear oils formulated from selected mineral base oils combined with a high quality sulphur-phosphorus extreme pressure additive to provide good wear protection, adhesion and cushioning of shock loads, reducing energy consumption. They have superior oxidation stability, demulsibility and retain their extreme pressure properties under severe operating conditions.

Texaco offers a full range of synthetic products ­ Synlube CLP gear lubricants are specifically designed for critical applications, based on polypropylene glycols and contain a special series of carefully balanced additives to give exceptional oxidation stability, rust protection, anti-wear and extreme pressure properties. These products have an inherently high viscosity index, ensuring absolute shear-stability and "stay in-grade" during the most arduous conditions.

Pinnacle EP, the polyalphaolefin based gear oil range has a very wide operating range, can withstand high temperatures and yet remain fluid well below ­35°C and thus provide good cold start properties. Pinnacle EP have an extremely low coefficient of friction which means in practice that system operating temperatures are lowered, and power consumption is reduced as is wear particularly during start up ­ all leading to long-term cost savings. Pinnacle EP products are fully compatible with mineral oils that may be left in systems after changeover.

To complement this range, a series of open gear lubricants is available. The Crater series is designed for the lubrication of open gears, bearings, wire ropes and chains in heavy, arduous conditions. They form a tough lubricant-film which will strongly adhere to moving gear teeth, will not squeeze out under shock loads, will not dry or flake-off and will resist washing off by water.

Rapidly gaining wider acceptance in the paper and continuous production industries is Texaco Coupling Grease. This product is formulated to avoid the oil separation that most greases experience at high centrifugal speeds as found in couplings. Due to its extra adhesive qualities Texaco Coupling Grease remains on the gear teeth, thus preventing wear even under high speed and high load conditions. Its superior resistance to oil separation makes it suitable for all types of flexible couplings as defined by AGMA Coupling Grease Specification CG1, CG2 and CG3.

Texaco supplies the commercial heavy goods vehicle market with a full range of automotive gear and transmission fluids to meet the most arduous service conditions.

The Geartex range (EPA/EPB and EPC) is available in a range of SAE viscosities to meet API GL 4 and GL5 specifications. Applications cover gearboxes, steering boxes, axles including hypoid, spiral-bevel, two-speed and double reduction rear axles as well as worm gears.

The automatic transmission fluid range includes Texamatic 7045 ­ a high quality product approved to the latest General Motors Dexron III (and Dexron II-E), Ford Mercon and Allison C4 specifications. Texamatic 7045 is formulated with selected highly refined base oils blended with a specially balanced additive combination to provide the desired frictional properties of an automatic transmission fluid.

Texamatic S manufactured from polyalphaolefin base oils and special additives is available. It is characterised by an extremely high viscosity index, providing improved lubrication under high temperature conditions and excellent low temperature fluidity. It offers the advantage of improved gear shifting, smoothly and without noise, both at high temperature drive, as well as under low temperature start conditions. Longer drain intervals can be considered as a result of the product's excellent oxidation stability, e.g. ZF-Ecomat Transmissions (90,000km) and Voith-Diwa (100,000km).

These Texaco lubricants are supported by a rapid oil analysis service ­ Texchek and a PC based lubrication scheduling device which is "windows compatible" called Computex Professional.

Further information is available from Texaco Lubricants, Sampson Street, Hanley, Stoke-on-Trent, Staffordshire ST1 5EZ. Tel: 01782 280444; Fax: 01782 205080.

Castrol industrial gear lubricants

Although mineral oil based lubricants with the appropriate additive treatment are entirely suitable for the majority of applications the ever increasing performance demands mean that these oils frequently are having to operate near their design limits. Synthetic lubrication technology offers the production engineer enhanced reliability, better performance and extended lubricant life.

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  The Castrol synthetic range includes:

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  Alphasyn T: a polyalphaolefin (PAO) oil originally developed for the paper industry where gear lubricants are subjected to hot and wet conditions. It has been formulated for gear boxes and centralised lubrication systems which run at high temperatures. There are viscosity grades from 32 to 1,000.

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  Alphasyn EP: a PAO oil for applications requiring extreme pressure performance as well as a low pour point, long life and reduced friction. Viscosity grades are 220, 320 and 460.

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  Alphasyn PG: very high viscosity index (over 200) polyglycol base lubricant for wide temperature range operation (up to 150°C intermittent) with freedom from sludge. Primarily intended for worm reduction gearboxes, it replaces the Alpha SN and Alpha PG grades.

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  Alpha Gel: a 00 grade semi-fluid polyglycol base for long life over a temperature range of from ­40°C to 130°C with reduced friction and minimised leakage in small and medium size gearboxes. The thickener is a lithium hydroxystearate soap.

Alphamax

Not a synthetic, but the latest technology in a mineral oil based gear lubricant, Castrol Alphamax gear oil has a new (non-sulphur/ phosphorus) extreme pressure additive and contains a friction modifier. It is claimed to give effective protection against micro-pitting, a type of surface damage found on gears often referred to as "grey staining" from the German Grauflecken. Alphamax is supplied in four viscosity grades 150, 220, 320 and 460. The lubricant has approvals from David Brown, PIV and AF Flender with others pending.

More details from Castrol (UK) Limited, Burmah Castrol House, Pipers Way, Swindon SN3 1RE. Tel: 01793 512712; Fax: 01793 513506.