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Jmacx suspension

By Mark Allen, 18 Sep 2015 Gear

Jmacx suspension

A bolt-in, wide-track, coil-spring rear suspension that improves the 70 series on a number of fronts. Bingo!

So you’ve forked out a wad of cash for Toyota’s hairy-chested 70 Series Land Cruiser.

Proud as punch, you sink the go-pedal to get a bit of noise from the V8 as you rumble away from the salesman. All good so far.

The 70 Series is no doubt one of the few remaining tough-as-nails, fair-dinkum 4x4s left to choose from. So you’re riding high in this Jurassic-era-inspired bucket of bolts with its coil-spring and live-axle front end, manly long-throw gearbox, low-range stick on the floor (where it should be), and a long leaf-spring rear end, complete with a narrow wheel track.

Then your bubble bursts. Everything was just too good to be true. You discover that the front-wheel track is 1515mm while rear-wheel track is 1420mm. What the? That’s a 95mm difference! Then, to rub a shovel full of salt into your wounds, the first time you load your manly Cruiser up, she sags and drags like a pound dog with worms. Oh, the humility of owning a 4x4 that handles terribly on road, fair-to-crap off road (depending on terrain), and can’t handle the weight that your mate’s wheelbarrow takes in its stride.

Jmacx -suspension -2With the rear wheels following a completely different line to that of the front wheels, Toyota has half-buggered what should be a champion 4x4. Sand driving is twice as hard; ruts, rocks and pretty much all uneven surfaces are harder to drive because of the narrow rear end.

Toyota widened the front track (up from 1435mm in the previous six-cylinder model’s front end) to squeeze a 90-degree V8 diesel under the bonnet. But why didn’t they throw a few extra inches into the rear end while they were at it? It was cheaper not to..
Leaf springs carry heavy loads, right? Unfortunately, the OE leaf springs on the 70 Series need to be replaced with aftermarket units to really tackle the job they were intended for – which is great for the aftermarket mob.

Enter Jmacx Off Road Solutions. Its hands-on owner, Jason McIntosh, is a mechanical engineer, an ex-V8-Supercar builder and a general problem-solving extraordinaire. After seeing his bolt-in, five-link rear-coil suspension kit, complete with replacement diff and axle housing, I was ready to sign on the dotted line within minutes of meeting him and I don’t even own a 70 Series Cruiser!

Jmacx -suspension -4This kit is worth a look for all 70 Series Cruiser owners who want to correct the Cruiser’s aforementioned shortcomings. It’s impressively designed, and it’s made with the highest-grade materials. It has also been engineer-approved via swerve testing and red-tape ticks.

Yep, the Jmacx kit rectifies the narrow rear-wheel track to match the front track of 1515mm. Plus, it allows drivers to stick to factory or aftermarket leaf springs or to opt for better riding coil springs.

That’s right, you can have a workhorse Cruiser with rear coil springs, complete with a five-link suspension set up – that’s upper and lower control arms and panhard rod; all heavy duty and adjustable. Included in the kit are external chassis-strengthening plates, control-arm mounts, coil retainers, bump stops, pin kit, brake lines and fixing hardware

Now, don’t think for a second that coil springs are a soft option for those who need to carry a load. No, sir, this kit allows a GVM upgrade to 3900kg. Coils can carry any weight – you just need to specify the correct spring rates to deal with the load. Also, with coils it’s easier to ‘build-in’ variable spring rates for a softer ride when the vehicle is empty and a stiffer rate when it carts cement bags, camping gear or heavy caravans. Air bags within the coils, or even a full air-bag replacement kit, are also available.

Jmacx -suspension -3Another advantage of this kit is that it reduces unsprung weight. A typical pair of Cruiser rear-leaf springs can weigh up to 130kg, compared to a pair of coils, which are about 14kg.

This reduction dramatically improves shock absorber workings, which leads to less shock fade and improved handling on all driving surfaces – the faster and rougher the track is, the more improvement you’ll see. The bolt-in brackets and associated components weigh about 50kg, but it’s not unsprung weight and it’s still lighter than the factory gear you just binned. So, you’ve effectively gained a little payload.

If you have ARB Air Lockers, TJM Pro Lockers, Eaton Lockers or Toyota factory lockers, they can all be slotted into the new diff housing. On Jason’s rig he has custom-fabricated a 6mm, 350-tensile steel housing with DOM six-inch braced axle tubes, and matching front and back wheel track.

The diff pumpkin is a laser-cut, pressed and welded, 350-tensile steel unit, and the new axles are 43/40 billet chrome-moly, heat-treated, long-splined full-floating items, claimed to be 200 per cent stronger than the originals. All standard ancillaries (wheel bearings, diff centres and brake lines) are simply removed from the OE housing and re-placed to the Jmacx unit.

Jmacx -suspension -5Given there are differences in factory leaf lengths between the 70 Series - 78 Troopy, 79 ute and 76 four-door wagon, Jason has ensured his kit will fit all model variants. Notably, all factory dual fuel tanks can remain in OE position.

The only item that will need re-routing is the exhaust system to clear the new suspension components. This is also a good time to upgrade to a custom Jmacx three-inch system. Jason’s kit includes either a mild-steel or stainless-steel mandrel-bent, three-inch system from the turbo back, as well as a high-flow cat and muffler.

Regarding the heavy-duty upper and lower adjustable control arms and adjustable panhard rod: they are all factory 80 Series Land Cruiser specifications, so too are the coil spring and shock absorbers (pin uppers and eye lowers). Regardless of whether you walk into a Toyota or Airbag Man aftermarket suspension supplier, all you need to ask for is 80 Series gear. 

Jmacx -suspension -6While on the point of coils and shocks – these are the only components that are not supplied standard in the kit. Jason reckons that, because there are literally hundreds of options to choose from, each customer deserves the right to get exactly what they want. Maybe you want brand A coils or brand B shocks to return a silky-smooth high-speed ride on those relentless outback corrugations. Or maybe you want heavy-duty load-hauling ability to cart your game-fishing boat on the weekend. The choice is yours.

Coils can flex more than leaf springs, but don’t think that coils or this kit are made only for weekend rock-hopping warriors. Nope, this rear-end coil-suspension kit works better on all road surfaces at all speeds. The ride will be more comfortable, safer and the handling will be more predictable on high-speed corrugations, rutted dirt tracks, sand and even long stretches of bitumen.

Of course, your coil-spring rate and shock-absorber combination will largely determine ride quality and weight-carrying ability. Given the availability of a progressively rated coil spring, it is easy to have the best of both worlds, regarding comfort and weight carrying.

Jmacx -suspension -1For off-road driving, another advantage of the rear-coil spring set-up is that ground clearance is improved. Generally, the lower-weight bearing leaves in the pack and the U-bolts are the lowest point under the vehicle. These can hook up while climbing over objects, but, with the coil replacement, these low points are non-existent and the new lowest parts are the lower control-arm ends.

RRP prices of the kits are: $5000 for the replacement differential and axle housing; $10,500 for the complete diff/axle housing and five-link bolt-in coil kit; and $980 for the three-inch (mild steel) $1200 (stainless-steel) exhaust kit. Prices include shipping and insurance within Australia. See www.jmacx.com.au