DIY Guide



10 Mechanical tips EVERY 4WDer should know! HOW TO DIAGNOSE & REPAIR YOUR 4WD AT HOME - YouTube

Working on your car at home can be tricky, but Jocko’s got you covered when it comes to worn bushes, blown shocks, driveline vibrations, diff backlash, loose wheel bearings, squealing belts, oil changes and a whole lot more!


We reckon there is three main things that can damage your 4WD. Driving over rough corrugated roads when heavily loaded, lack of maintenance and consistent hard off-roading on tough tracks.

When you modify a 4WD with bigger tyres and suspension, areas like the driveline will wear out a lot faster in comparison to a stock vehicle.

We are going to show you the most common parts of your 4WD that will wear and fail, how to diagnose problems before they arise as well as tips on maintaining and fixing these problems in first place!


Tail Shaft

One of the most annoying things to deal with when driving is having a worn-out tail shaft. This causes driveline vibrations which can be very frustrating.

Bad tail shafts can be caused by hitting rocks or logs when out on the tracks or failing universal (uni) joints, which can happen after a long service life or driving in lots of watery and dusty conditions as both can make their way into the uni joint and contaminate the grease. This again can lead to failure by creating excessive heat.

Having larger tyres and doing some tough off-roading puts a lot of stress on your 4WD’s old joints particularly during a lot of stop-start driving with excessive wheel speed.

tail shaft damage from 4WDing

Inspection of the driveline

With the vehicle in neutral and safely secured with wheel chocks so it won’t go anywhere, inspect the shaft for any dents or gouges as these will affect the balance of the tail shaft and cause vibrations.

Next give each end of the tail shaft a shake to check the uni joints. Worn out uni joints will move excessively and will need replacement to avoid future failure. Do the same shake test with the slip joint as well.

It is a smart thing to check over your front and rear tail shaft every service or every 10,000km and re-grease if required. Also inspect them when you get home from a 4WDing trip if you have done river crossing, mud bogging or spent a lot of time on long dusty roads.

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Axles and Constant Velocity (CV) Joints

Breaking an axle or CV joint can be difficult to diagnose particularly in a solid axle vehicle unless you’re watching the vehicle drive off road and you hear a loud bang followed by a loss of drive to a particular wheel.

If the CVs are worn in your vehicle, one way to check is to turn at full lock with the vehicle in 4WD. if you hear a clicking sound coming from your front end then your CVs are worn.

Axles usually fail from aggressive driving style, larger tyres causing excess stress on the driveline and years of use causing fatigue and wear followed by shock loading.

For example, if you are out 4WDing and a wheel is spinning in the air and quickly regains contact to the ground, that shock load often causes a CV or axle to fail, particularly ones that have had a long life.

If you drive an IFS vehicle, the easiest way to know if you have blown a CV is that there will be grease and ball bearings all over the track.

CV damage controlled driving compared to shockload


Differentials (Diffs) are one of the more expensive areas to maintain if they do fail, and they need to be set up properly by a reputable diff specialist who knows what they are doing.

Excess wearing of your differentials can usually be narrowed down by listening out for clunking or whining particularly as you drive and you are on and off the accelerator, also at higher speeds as well.

The colour of your diff oil will tell you everything you need to know. If the oil is milky, it indicates water has contaminated the oil. If it is dark grey, then the oil either hasn’t been changed in a while or the diff is wearing out. If there are large chunks of metal coming out with the oil, then it is a safe bet to diagnose that you have some chipped teeth off the crown wheel or pinion.

Another way to check for wear on your differentials is to have the opposite end of the diff you are checking’s wheels chocked so the vehicle cannot move, and it is in neutral. With your hand try and lightly rotate the tail shaft in both directions. If there is a bit of movement and you can hear some clunking internally then that is usually a sign that there is excess backlash in your diff, and it will need a rebuild at some point soon.


Wheel bearings have a hard life and get up to extremely high temperatures particularly when driving around with big tyres and when doing lots of kilometres.

Common causes for failure are things such as: water ingress, lack of maintenance, bigger tyres, larger wheel offsets as well as bearings coming loose over time. All this causes more heat and reduces service life of the grease inside your hub, therefore reducing the service life of the wheel bearings.

Shauno Graham Jocko 4WD


The reason people fit larger offset wheels is it allows you to fit bigger tyres as the tyre isn’t sitting in the guard as much. It gives you a wider stance for stability off-road and makes your 4WD look tougher.

Putting bigger tyres and larger offset wheels puts a lot more stress on your bearings. From factory your wheels are bolted nice and close to your wheel bearings, and if you add a greater wheel offset you are moving it further away from the bearings and creating leverage. Add that to a bigger tyre and there is even more force on the bearings causing more wear.

larger offset tyres and space in wheel arch

Regular inspections and repacking are the best ways to keep on top of your bearings. The easiest way to check is to jack up your vehicle and secure it on axle stands and put your hands at 12 and 6 on the tyre. Rock the tyre and wheel back and forward and if there is any movement your bearings need inspection, repacking or tightening.


Wearing down suspension bushes usually happens from a long service life. Running bigger tyres, a larger lift, getting more travel out of your suspension or even just using the wrong type of bush for your suspension set up can make these bushes wear down much faster

Worn out bushes can often be diagnosed by clunking or movement in the driveline. Another way to tell is if a vehicle moves around on the road under acceleration or deceleration. If you must fight to keep the vehicle in a straight line it is usually a sign you may have worn suspension bushes.

Get yourself a pry bar and go underneath your 4WD and work your way around all the areas in your vehicle that use a bush set up. Lever the pry bar in and try to get a bit of movement out of the arm, and if you can move it then that is a sign the bush is worn and needs replacement.

Coil and Link Suspension

When you lift your 4WD, you change the angle of the trailing arm and what that does is creates more leverage on the bushes in the arm. In fact, when you hit bumps that force is further increased and wears down your bushes faster.

Leaf Springs

With leaf springs, like in dual cab Utes, the idea is very similar to above. If you add a heavier leaf pack, then there is much less give in the suspensions which means that force when you hit bumps goes through the springs and wears out your bushes faster – particularly if you have a heavy leaf pack and aren’t carrying much weight as they will be much stiffer.

Another trick is to get a mate to crouch down and watch the vehicle as you drive forward and back. They can see if any arms move as you stop and can also listen out for clunking noises as well.

Panhard Rod

If your vehicle has a Panhard rod, its job is to control the side-to-side movement of your diff on a solid axle vehicle. If your bushes are worn at either end of the rod, you will get a lot of steering wobbles.

Worn Panhard bushes are often caused by extreme angles on the arm from large suspension lifts and wear and tear on high kilometre 4WDs.

Easiest way to diagnose it is to have a friend turn the steering wheel side-to-side as you watch both bush ends. If there is any movement at all then replace the Panhard bushes.

Tie Rod / Drag Link Ends

Whether your 4WD is IFS or solid axle, the main thing you should keep an eye on are your tie rod end or drag link ends. Basically, it is a ball joint with a boot and inside has a bit of grease.

tie rod end drag link end and boot

They are under a lot of stress as each time you turn the wheel these are what turn the steering knuckle. With big tyres means even more force is transferred through those tie rod ends and drag link ends when you hit a bump.

If these boots are split, then replace the end. This can cause bending of the steering arm and can create a nightmare of a bush mechanic trackside fix without a spare.



A worn spring will move through its range of motion easier because the metal in the spring has fatigued and the spring has become softer. This means that as you drive on rougher roads, your bump stops will hit the chassis more frequently and overtime can cause fatigue in your chassis. Worn out suspension will lead to a much more uncomfortable ride.

The simplest way to diagnose worn out suspension is to see how your vehicle is sitting. Older leaf sprung 4WDs will tend to lean over to one side as the suspension starts to sag and the spring flattens out.

If your spring rates are incorrect for the load you carry, this can also speed up your springs wearing out as they weren’t physically designed for what you want them to do.

Shock Absorbers

When it comes to shock absorbers in your 4WD, they can massively impact how your vehicle drives and its performance.

The biggest killer of a shock is overheating, usually happening from driving on rough corrugated roads for a long period of time or even harsh off-roading, particularly if you have a poorer quality shock absorber.

A vehicle that feels spongey and bounces around a lot when driving can indicate bad shocks. If a shock is leaking, it also means the seal has failed. Shocks have liquid, gas or sometimes both in them and once a seal fails the easiest fix them is to replace – unless you have a rebuildable shock, then just put in a new seal kit through.

Another way to see if your shocks have failed is to bounce the vehicle at each corner and watch it recover. If it keeps bouncing it means your shocks require attention.

The best way to prevent early suspension failure is to ensure you fit the correct springs for the load you intend to carry in your 4WD, that way your suspension is designed to handle the weight and put less stress on your driveline when you load it up.


Common causes for failure within your 4WD’s gearbox are high kilometre vehicles, lack of maintenance, heavy towing in the wrong gear – such as labouring the vehicle with a heavy trailer in 5th gear up a hill.

 Another tip is if you drive manual, don’t drive with your hand resting on the gear stick. Doing that wears down the selector fork inside the gearbox, and over time it will be harder to shift gears.

Grinding and crunching when going into gears can indicate bad synchronizers, and if the vehicle also jumps out of gears can also mean bad synchronizers or contaminated oil.

Like with your diffs, draining your oil will give you a good indication of the conditions of your gearbox as well.


One of the biggest killers of any automatic transmissions is heat that can usually come from something as simple as fitting bigger tyres, towing a heavy load or even something like not having a big enough transmission intercooler. All these things can put excess stress on your 4WD’s auto transmission.

Here are some tips from a familiar face, the Automatic transmission Guru, Rocket Rod, from Wholesale Automatic Transmissions:

-          Service your auto transmission regularly, recommended every two years or 50,000kms. You need to replace the oil pan gasket and oil filter.

-          Install an auxiliary oil cooler. Highly recommended addition to any vehicle, especially 4WDs and ones that tow. This not only helps avoid overheating, but it also extends the longevity of the oil and the oil seals. The life of an automatic transmission can grow an extra 100,000-200,000kms if you reduce the difference between how cold it gets in the morning and the normal running temperature. The hot and cold cycle is also what makes seals go brittle.

-          Temperature gauge. We recommend an aftermarket temp gauge – either a scan gauge or dedicated transmission temp gauge – rather than relying on your stock dash temperature light. This will teach you so much about your transmission, and you will quickly learn what your 4WD does and doesn’t like. After a period of time you will be able to pick up when something is not quite right with your transmission and you will figure out when backing off or changing gears will help via the temp gauge.


The best way to ensure your engine lasts a long time is to do regular oil and filter changes. This will also let you inspect the oil and regularly keep an eye on it if anything is going on.

Jocko changes the oil and filters of his Hilux every 5,000kms, and the oil, filter and fuel filter every 10,000kms.

Engine Smoke

One of these easiest ways to see if your engine is sick is if it is blowing any smoke, and at what point does it smoke.

Blue / Grey Smoke

Bluish grey smoke is usually burning oil, which can range from valve stem seals to worn piston rings, which allows oil into the combustion chamber.

For example, if you see a bit of blue smoke that comes with a quick jab of the throttle, that can usually indicate something like worn valve stem seals in a petrol engine. But if you notice it a fair bit of blue smoke when under excessive load (like accelerating up a long hill) this can indicate worn piston rings.

Blowing smoke in diesels is much more common.

White Smoke

White smoke is generally from a problem with combustion and fuel. It can range from fuel not being burnt correctly to something like poor spray pattern from an injector to a turbo seal failure or even extreme cases of coolant making its way into the combustion chamber due to head damage.

Black Smoke

Black smoke is often simply excess fuel or excess carbon build up in the EGR or intake.

Cooling System

You can have the best engine in the world, but if you don’t keep it cool it is going to cause you dramas. Your factory temp gauge may not move straight away if your temperature goes up.

Cooling System Checks

If you think your engine is running hot, do some easy checks first. Make sure your radiator isn’t blocked with mud.

After taking your 4WD for a drive, before you turn it off, open the bonnet and keep an eye on the engine fan. Shut the engine off and check to see if the fan keeps spinning, and if it does it can indicate a worn viscous hub. This means your fan won’t be pulling air through the radiator as much as it should.

Another tip is to check your radiator cap. This is commonly overlooked, but if these fail it can cause your whole cooling system to overheat. A good thing is to check the spring operates correctly and it is holding pressure in the system. If you are doing a cooling system service, it is a smart idea to simply replace it.

two guys on a car


The general theme of this DIY mechanical advice article is that the more you modify your vehicle with bigger tyres and higher suspension lifts, the faster the mechanical components are going to wear down.

Having said that, don’t let this stop you from modifying your 4WD, because we do all of this so we can get out on the tracks, explore and have fun!

As long as you are aware of these potential issues and keep on top of maintenance, you’ll have a reliable 4WD that will last for years to come.

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