How to check and replace the diff oil of your Hilux

This tutorial shows how easy it is to check or replace the diff oil of your Hilux. I did this on the rear diff of my 2.7 Hilux but the procedure will be the same for most other diffs. If nothing goes wrong this should not take you longer than 20 minutes.

Checking the oil:
You will see that the diff has two plus. On my vehicles both plugs take a 24mm spanner. It is better to use a socket than spanner.

The plugs' heads are very thin and you can damage the head easily if you are not careful. It is advisable to first take a hammer and hit the head of the bolt/plug on the flat surface a couple of times first. This will help to get it loose. Just hit it lightly and be careful not to damage the sides of the head. This trick works especially in a case where you have a metal plug on an aluminium casing.

If you can still not get the plug loose you can also try a bobbejaan spanner, vice grip or even weld the head of another bolt onto the head of the plug. Remember to disconnect the battery before you weld on a vehicle. (Thanx for this one Simon)

The plug on the back of the diff housing is the inspection/filler plug and the one at the bottom is the drain plug.

Remove the drain plug by turning it in an anti clockwise direction. As I said it is best to use a socket. I bought my vehicle second hand and the plug has been damaged by the agents where the previous owner had the vehicle serviced. If the plug is damaged you can try to hit it loose with a chisel or use on of the tools shown in the picture below.

In my case I first tried the chisel and in the end the tool in above picture did the job.

Once you removed the inspection plug put your little finger in the hole. The oil must be level with the bottom of the hole. If you can feel the oil with your finger the level is OK. If not you have to top it up.

If the oil has a white-ish or grey colour it means that it has been contaminated with water and you will have to replace it.

If your vehicle is old and you are not sure when last the oil has been changed, drain the oil and replace with new oil. It won't hurt to change the oil every 100,000km or so. Your vehicle's manual will also tell you how often to change the oil. Some guys say as often as 40,000km.

Replacing the oil:

If you have to replace the oil, remove the drain plug. Remember to put something under the diff to catch the oil. It must be big enough for just over 2 litres of oil. I always use an old empty 5l oil can of which I cut the side open.

Unless you want to replace all diffs and gearbox's oil at the same time it would be best to rather buy the small 500ml bottles. Even if you buy a 5l can you must still buy at least one 500ml can. The reason is that the small can has a nifty little pipe thing inside which makes it easy to put the oil into the diff or gearbox.

I know there are huge discussions on the correct type of oil. I do not want to get involved in those discussions. I believe that if my grandfather's bakkie could do more than half a million kilos using normal non-fancy oil, so can my vehicle. So I just use any good old 80W/90 hypoid gearbox oil. Today Indy Oil's 80W90 Hypoid Gear oil did the trick for me.

Note that:

1. You will use the same oil for both diffs and your manual gearbox. Automatic gearboxes use a different oil. The process to check and replace your manual gearbox oil is the same as for the diff.
2. If you diff has a Limited Slip Diff (LSD) like the Nissan Terrano, some Toyota Surfs, etc then you must use the oil for the LSD. Normal gear oil will render your LSD useless.

Once all the old oil run out, replace the drain plug and tighten it. Do not over tighten. You will note that the drain plug has a copper washer. If you have the time go buy a new copper washer. It is not compulsory, if you do not stuff it up you one copper washer can do the work for very long.

Once you replaced the drain plug you can start to refill the diff. Most diffs for small vehicles like a bakkie will take roughly between 2 and 3 litres of oil. Most Hiluxes takes between 2.2 and 2.3 litres. The exact quantity does not really matter in this case because you have to buy 5x 500ml anyway. So whether it uses 2.2 or 2.3 litres you still have to buy 5 of them.

With the inspection/filler plug still removed you can now stick the pipe of the oil bottle in the hole and squeeze it.

Repeat this squeezing thing with all the bottles un till the oil starts running out of the hole. As soon as this happens you know there is enough oil in the diff and you can replace the inspection/filler plug.

That is it. Easy hugh?