DIFFLOCK - 5 speed box Oil change

First make sure you are wearing your Finite Synthetic Nitrile Gloves. These are essential to stop your skin coming into contact with diesel fuel, old oil and other contaminants that can cause a variety of skin complaints or chemical burns.

Locate the main manual gearbox filler plug and loosen it using a 1/2” AF spanner (LT77 Gearbox) or T55 torx bit (R380 Gearbox) and position a Drip Tray and Oil Drain Pan beneath it. In the picture below, showing an LT77 box, the square filler plug is numbered 1.

Remove the filler plug but watch out for a dribble of oil.

DIFFLOCK TIP: Note that the filler plug is in a very awkward location and it will be impossible to get any oil into the box without a flexible tube. We recommend you purchase either an OilSafe Pump Kit or a Fluid Transfer Pump to make life easy

In this picture of the LT77 gearbox the square filler plug (1) can be seen above the large Hexagonal drain plug (2). The R380 box is similar except the filler plug requires a T55 Torx bit to undo it

Using a 32mm Wrench (there isn't room for a socket to be fitted) Loosen the main gearbox drain plug but do not remove it yet. Reposition the drip tray and drain pan under the drain plug but bear in mind that when you remove the drain plug the gear oil will first shoot out horizontally before gradually falling back to drain out directly beneath the drain hole. Usually it runs down onto the chassis cross member and then spreads out to drip off quite a wide area so you really do need a wide drip tray and drain pan.

When you have your drain pan in place unscrew the loosened drain plug by hand BUT keep the plug pressed firmly against the gear case at all times as you unscrew it. When you are satisfied that there is no more thread, just your hand pressure holding it in place, then double check your drain pan is in position and whip away the drain plug as fast as you can so that your arm is not covered with oil as it gushes out.

Here the old ATF fluid can be seen draining from the extension case on an LT77 gearbox. Note its characteristic red colour and very thin viscosity

While the oil is draining wipe any debris off the drain plug. It is magnetic and usually it acquires a little ‘hedgehog’ of iron filings. This is quite normal and nothing to worry about, however if any large chips of metal or gear teeth are present on the plug or in the drained oil this indicates some internal damage has occurred in the box.

A ‘hedgehog’ of iron filings such as can be seen on the left hand drain plug is normal and not cause for concern. Larger lumps or chips in the drained oil might require further investigation. On the right can be seen the same drain plug after the filings have been wiped off.

Once all the oil has drained out replace the drain plug (preferably using a new copper washer) and tighten. The correct torque is 50NM but since a socket and torque wrench can't be used you should tighten carefully by hand. It may be useful to apply a torque of 50NM to a spare nut and bolt so you can gauge what this torque feels like before applying a 32mm spanner to tighten the drain plug.

If you have an earlier LT77 box you now need to reposition the drain pan underneath the extension case drain plug, its hole drains out vertically so the bowl can be positioned directly underneath it. Note: Later R380 boxes do not have this second drain plug.

The extension case drain plug also incorporates a plastic filter that is about 100mm long and this must be withdrawn with the plug. Using a 24mm Socket or Spanner loosen the drain plug and remove by hand. While the oil is draining turn your attention to the filter. Flush it out with white spirit or paraffin and examine the mesh carefully. The filter should be cylindrical in shape with no twist and the mesh should be uniform with no rips.

This plastic filter sits above the extension case drain plug in the LT77 box and must be cleaned whenever the oil is renewed. An old toothbrush and a little white spirit are ideal for cleaning the filter prior to refitting it.

Wipe off any debris from the drain plug and once all the oil has drained out replace the filter and plug (preferably) using a new copper washer. The plug should be tightened to a torque of 50NM.

The gearbox can now be refilled with Difflock Evolution 1 Fully Synthetic 5-Speed Gear Oil or Difflock ATF Type DIII through the filler plug.

Fill the gearbox until oil starts to run back out of the filler hole, it should take around 2.7 litres before this happens. Wipe any debris off the filler plug and refit it, tightening to a torque of 25NM. (DO NOT OVERTIGHTEN since the plug thread is a taper variety and will damage the gear case if too much torque is applied).

Replacing Oil in LT230 Transfer Gearbox

Locate the transfer gearbox filler plug (numbered 4 in the picture) and loosen it using a 1/2” drive extension bar inserted into its square recess. Position a drip tray and oil drain pan beneath it.

Never, ever undo a drain plug until you have undone the corresponding filler plug FIRST. That way you are absolutely sure to be able to refill with fresh lubricant after you have drained all the old oil out!

Remove the filler plug but watch out for a dribble of oil.

Locate the transfer gearbox drain plug (numbered 5 in the picture) at the bottom of the sloping section under the hand brake drum.

Using a 17mm Socket or Spanner loosen the transfer gearbox drain plug but do not remove it yet. Reposition the Drip Tray and Oil Drain Pan under the drain plug.

When you have your drain pan in place unscrew the loosened drain plug by hand BUT keep the plug pressed firmly against the gearcase at all times as you unscrew it. When you are satisfied that there is no more thread, just your hand pressure holding it in place, then double check your drain pan is in position and whip away the drain plug as fast as you can so that your arm is not covered with oil as it gushes out.

While the oil is draining wipe any debris off the drain plug. If any large chips of metal or gear teeth are present on the plug or in the drained oil this indicates some internal damage has occurred in the box.

Once all the oil has drained out replace the drain plug (preferably using a new copper washer) and tighten to a torque of 30NM.

The gearbox can now be refilled with Difflock Evolution 2 Fully Synthetic Gear Oil or Difflock Hypo EP80W90 through the filler plug.

Fill the gearbox until oil starts to run back out of the filler hole, it should take between 2.3 and 2.8 litres (depends on model year) before this happens. Wipe any debris off the filler plug and refit it, tightening to a torque of 25NM. (DO NOT OVERTIGHTEN since the plug thread is a taper variety and will damage the gear case if too much torque is applied).

Synthetic Gear Oils

If you haven’t already heard about our fantastic range of Fully Synthetic Gear Oils then you don’t know what you are missing.

Our highly advanced Fully Synthetic technologies will:

Fully Synthetic Gear Oils also last up to three times longer than mineral oils before an oil change is required.

Just what makes our 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 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.

A Sound Investment

If used in both the axles and the main and transfer gearboxes of your Land Rover, our synthetic gear oils will typically give a three percent improvement in fuel economy.

This might not sound much but take a look at the maths:

• Fully Synthetic Evolution 1 and Evolution 2 will last for at least 48,000 miles before they need to be changed (double the mileage of plain oils).
• Over the full 48,000 miles at 30 mpg a Diesel Landrover will use 1,600 gallon of fuel or 7,273 Litres
• At 76 pence per Litre for Diesel the fuel cost would be £5,527
• A three percent saving on this total amount equals £165
• Total cost of Evolution 1 and Evolution 2 for axles and gearboxes equals £62
• Typical overall saving over the lifetime of the oil is a whopping £103!!!! And could be as much as twice this if you have a V8 petrol vehicle!!!!

You don’t have to take our word for it either, you can read the excellent feedback received from our delighted customers by looking at the product pages for Evolution 1 and Evolution 2 in our online store.

Replacing Oil in 5-Speed LT77& R380 Manual Gearbox

Replacing Oil in LT230 Transfer Gearbox

Synthetic Gear Oils