I agree completely that both the LT77 and R380 box have design deficiencies. Equally our MT75 lubricant is indeed, overcoming some of these deficiencies but its not unusual to use a lubricant in this manner. A lubricant is after all, an integrated part of the transmission system and ideally, its properties should be selected to give the best possible results given the mechanical limitations of any transmission.
Equally I understand your healthy scepticism in this day and age of exaggerated marketing claims. All I can say is that the comments posted on our site, the Difflock Forum and the LRO forum are from genuine customers who have used MT75 and have provided the feedback, unsolicited from us.
Equally, we did a great deal of research before selecting our lubricant range, including visiting the blending plant and laboratories of our supplier.
You can buy MT75 from our online store and we ship worldwide including the Middle East.
Here's some more useful background on Transmission Lubricants which may help explain why synthetic lubricants (of the correct viscosity) are far superior to their plain mineral counterparts and why our very low viscosity MT75 fully synthetic oil produces such excellent results in LT77 and R380 boxes.
Transmission oils have two main functions:
The first function is to minimise friction and hence wear.
They do this by the nature of the base stock (the actual oil) itself which is naturally 'slippy' but also by the use of extreme pressure (EP) additives which chemically bond to the metal surfaces when the metal to metal contact produces high temperatures due to friction. This layer of EP chemicals acts as a sacrificial agent which shears down preventing potential welding of the metal surfaces in contact with each other (another reason why Gear Oils should be changed at the vehicle manufacturer's recommended intervals)
Such Oils are normally rated as either API GL4 or GL5.
In Simple terms, GL4 contains a certain concentration of EP additive, whereas GL5 oils contain twice the amount.
API GL4 oils are used where moderate loads are experienced - Typically certain manual transmissions.
API GL5 oils are used where high loads and speeds are encountered – Typically differentials, final drives etc.
Interestingly, some applications give rise to difficulties with EP additive oils. A notable example is the 4 speed manual Range Rover Gearbox where (with a standard tune engine) the gear loading is not severe enough to require the levels of EP additives found in GL4 or GL5 oils. Here then an engine oil is recommended and used instead.
If you own an older generation vehicle such as a Series Land Rover you must be VERY careful about selecting your transmission oil. This is because certain Extreme Pressure additives containing Molybdenum compounds can give rise to copper leaching and so these will attack the soft metals, such as brass, found in Series Transmissions.
As far as metallic leaching is concerned, whether an oil is GL-4 or GL-5 is only relevant in that GL5 typically contains twice the concentration of additives as GL4. Hence IF a GL5 oil contains the problem Molybdenum compounds then the leaching action will be faster. However both GL-4 and GL-5 oils can be formulated without the problem compounds so the GL rating is not strictly relevant. Note though that the mineral or synthetic base stocks (the oil itself) of a lubricant will not attack soft metals so it does not follow that Synthetic Gear Oils are bad for older transmissions.
Only the lubricant manufacturer (and hopefully your supplier so ask them!) will know whether the problem Extreme Pressure Additive compounds are used and if these are in sufficient concentration to be problematic in certain transmissions.
The second function of transmission oils is to disperse heat.
Special additives are incorporated to prevent highly localised build up of heat within the gear oil. Without this the oil would rapidly oxidise (and lighter fractions in the blend evaporate) gradually increasing the viscosity of the oil and leading to sludge.
Equally the oil has to be of a low enough viscosity to flow around the gearbox in sufficient quantities to disperse heat build up.
Now lets return to the original question of why Land Rover 5 speed boxes require a low viscosity oil.
As with most lubricants, the viscosity is a critical factor in the lubricants performance:
Too thin and the oil film will be insufficient to prevent metal to metal contact.
Too thick and the lubricant will slow down the gearing mechanism (leading to poor and notchy gearchanges) and not disperse the heat generated quickly enough.
Those of you with a Land Rover 5 speed box will know that the gear changes are not slick, especially when the oil within is cold (and at its thickest). So Land Rover has opted for a thin 5W/20 ATF type fluid in order both to improve the action of the synchromesh and provide for good heat dispersal, but with the penalty of poorer metal to metal lubrication.
Now lets consider the benefits of Synthetic Gear oils as opposed to their plain mineral counterparts:
Highly advanced Fully Synthetic technologies will:
1. Eliminate notchy, slow and hesitant gear changes, especially from cold
2. Improve fuel economy
3. Reduce gearbox wear
4. Reduce whine and transmission noise
5. Lower transmission temperature
Fully Synthetic Gear Oils also last up to three times longer than mineral oils before an oil change is required.
Just what makes Synthetic lubricants so superior?
Well unlike ordinary mineral oils such as ATF, EP80 and EP90, Fully Synthetic Gear Oils are far less susceptible to either selective evaporation at high running temperatures, or viscosity variations due to changing ambient or working temperatures (especially on those cold winter mornings). Hence they better maintain an optimum, stable viscosity and have improved flow characteristics at all temperatures.
They have a higher film strength too, which means they are less easily squeezed out of extreme pressure contact areas found on gears and in bearings.
These benefits actually reduce transmission temperature and improve economy since frictional losses become lower. Lower friction also means less noise and so Synthetic Gear Oils are excellent at reducing gear whine and bearing noise.
Synthetic oils are also less prone to aeration (foaming) and this means the lubricant stays more concentrated and evenly distributed throughout drivetrain components.
So those who have switched to Fully Synthetic Oils in your LT77 or R380 5 speed manual gearboxes are indeed very wise to do so. However, by choosing a less than optimum viscosity such as 75W/90 you will not be gaining the full benefits from such oils, namely dramatically improved gearchanges, better heat dispersion and improved economy (typically 3% if synthetics are used throughout the drive train).
Fully Synthetic 75W/90 is of course, excellent for use in transfer boxes and axles on Land Rover vehicles where operating conditions and lubricant requirements are different to those of the main gearbox and a thicker viscosity is specified. (Note the Range Rover Borg Warner Transfer Box requires a 5W/20 viscosity oil).
However, for the main 5 speed gearbox you should be using a Fully Synthetic 5W/20 viscosity gear oil such as our MT75 for best results.
You can find the entire range of both Synthetic and Non Synthetic gear oils mentioned above (including oils compatible with older transmissions and 5W/20 Fully Synthetic MT75 Gear Oil) for sale in the Difflock.com store.
Please feel free to contact me directly if you would like any specific advice on Lubricants and Lubricant Selection.