Welcome to Jmacx

Australia’s leading suspension specialists for the Toyota Landcruiser and innovators of the bolt in coil conversion , we have you covered from leaf to coil suspension with the highest axle load rating in Australia , GVM upgrades from 3900kg to 6000kg and legal lift of up to 4 inches and 35 inch tyres , have a look through our website to find a product that best suits you.

LC70 Series 3900 GVM Coil Conversion

The Jmacx 3900 GVM bolt in coil conversion is the world’s number one trusted bolt in coil conversion on the market and is the industry leader here’s why, with hundreds of conversions done and millions of combined kms driven in some of the worlds harshest condition this kit is fully engineered to go above and beyond. Also giving you a GVM upgrade of 3900 this is the ultimate suspension upgrade for outback tourers, commercial vehicles and the weekend warrior. Tested and proven in some off the world’s harshest conditions.

  • all Jmacx bolt in coil conversion can be done *PRE AND POST REGO* in all states
  • all Jmacx bolt in coil conversion can have up to 4inch of lift and 35inch tyres
  • with this Jmacx bolt in coil conversion you get a:
  • Increase GVM to 3900kg
  • Maintain BTC of 3500kg at full 3900 GVM
  • Axle load increase to 2700kg 
  • SSM Number:48554 (visit rvcs website to confirm Specs)
  • (for more information on axle loads,BTC AND GVM please read our article here CALCULATE YOUR WEIGHT)

All Jmacx products have full engineering to ensure you are safe and legal on Australian roads. To see what comes in your Jmacx bolt in coil conversion please watch the video and then use the kit builder bellow to get a quote today.

Frequently Asked Questions


When it came to choosing and engineering a replacement rear suspension system for the 70 series Landcruiser there was a few different geometry’s to build off but only one was superior from all of them and this was the 5 link set-up.

The 5 link suspension system has been used by all Major vehicle companies for many years now for example 80/100/105 series landcruiser , Nissan NP300 and Patrol GQ/GU , Dodge Ram , meaning it has been tested and proven itself as a capable geometry set-up .

The biggest advantage to the 5 link suspension set-up is its load carrying ability from the REAR PANHARD ( the 5th link ) this allows the rear differential to stay fixed and stabilised when cornering or with any side load on the vehicle , without this rear Panhard the differential would be able to move freely side to side from the chassis this would be suitable for light vehicles with low centre of gravity , rock crawling 4wd or a drag car that needs to only go in a straight line .

However when it comes to a heavy load carrying vehicle this would not be safe as it would not be able to support the side load on the suspension set-up hence where the 5 link came out on top the 70 series is a load carrying vehicle with a high centre of gravity so the rear Panhard is a must to keep the suspension centred.

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The 4 link Suspension system was another common geometry set-up that we looked at in the beginning however it had some major draw backs we it came to applying it on a 70 series land cruiser. Here is why Referencing straight from the BOSCH Automotive Engineering Handbook Version 7 – 9 on what is needed”

‘’The basis of what is considered appropriate is based upon stability and other kinematic effects on the road handling of the vehicle.

4 link suspension system are acceptable in the correct circumstances and with the correct application of the engineering to ensure stability of the systems.

The basic 4 link suspension system is designed for certain applications which are generally of high articulation applications ( Rock Crawling off-road vehicles , high monster truck types, performance cars , hotrods or very rigid suspension applications).



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The following are the critical design aspects for 4 link systems.

  • Link lengths
  • Instant centre (intersection point)
  • Anti-squat geometry percentage
  • Axle angle change

Note: Intersection Point is a very important aspect and provides the balance to the system.

With regards to running the 4 link setup on a 70 series land cruiser, it is not possible to run triangulated lower control arms as the diff centre is not centralised meaning you would have to use straight lower control arms this setup is far from ideal for a road going vehicle. The system should ideally be a double triangulated setup with both upper and lower control arms at opposing angels to ensure that the system can be centred at all times.

With a straight lower control arm, the axle housing is able to laterally traverse under heavy load cornering, or indeed towing (ie: will try and maintain its original track and then dynamically release to follow the vehicle and as such causes a significant amount of instability and can be catastrophic if coupled with a incorrectly loaded trailer ).

The images provided are considered an appropriate system with a double triangulated setup,


 Does the Kit Contain Parts that are Custom and Maybe Difficult to find if in the middle of Nowhere?

  • Our diffs maintain all factory brakes, hubs, bearings, seals, diff lockers etc.
  • Our Coil Kit uses factory length Landcruiser control arms, Panhard.
  • Most parts maintain OEM Toyota bushes, so parts can be easily accessible anywhere in the world.

What if I Break an Axle?

  • Our diff housings are full fabricated units that exceed the strength of the factory original unit. JMACX Axles are the strongest production manufactured axle for Toyota Landcruiser available.

How Long will Jmacx need my vehicle for?

  • The Conversion will take around 7 working days depending on what accessories are being fitted to the vehicle .

 Does the new wide track diff correct the rear vehicle track?

  • Yes

Can i have a Custom Colour?

Yes, automatically our kits are a standard black.

But let us know and we can give you a custom colour to suit you!

We often see customers selecting a colour that represents their business 

Will It Affect my Insurance?

No, but it is up to each individual to check with their insurer. (Generally Insures only require the vehicle to be Legal.) 




LC70 Series 3900 GVM Leaf Spring

Jmacx now has a leaf sprung gvm option for the landcruiser that ticks all the boxes. track correction, higher axle load capacity, improved braking, vehicle stability. All though the leaf spring kits can’t compare to the ride comfort of a coil conversion they are a great option for those who want to stay with the leaf springs and need a true and usable 3900 GVM upgrade kit. Here are some key points as to what you can get from a Jmacx 3900 leaf kit.

  • Increase GVM to 3900kg
  • Maintain BTC of 3500kg at full 3900 GVM
  • Axle load increase to 2700kg
  • This kit can come with either 300kg  or  300kg – 500kg leaf packs
  • SSM Number:50368(visit rvcs website to confirm Specs)
  • (for more information on axle loads,BTC and GVM please read our article here CALCULATE YOUR WEIGHT)

The biggest advantage to the Jmacx 3900 leaf kit is the high rear axle load capacity of 2700kg this combined with the GVM upgrade allows your landcruiser to be loaded practically in the rear to its full potential.   

All Jmacx products have full engineering to ensure you are safe and legal on Australian roads. To see what comes in your Jmacx 3900 leaf kit use the kit builder bellow to get a quote today.