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M A R K S P O R T A L A X L E S>

product test

portal CallSo you want more ground clearance? Real, improved ground clearance? Portal axles

are the only way to go!

ortal or drop axles have been around for years, but we’ve seen very few in Australia. Highly respected and very capable European 4X4 vehicles such as the Pinzgauer, Volvo and

Unimogs have sported them for ages. Now, with aftermarket kits available for Nissan GQ and GU Patrols and late-model solid-axle LandCruisers, the scene is set to change here in Australia.

Marks 4WD Adaptors has designed and manufactured a portal axle kit for the Patrols for more than three years now, while the Cruiser kit has just been completed. The Patrol kits have under-gone extensive proving and testing – Cruiser currently – and have been approved in most states by the relevant road traffic authorities.

So what are portal axles? Generally, a portal axle assembly is a solid axle which incorporates a hub reduction gear-box assembly just inboard of where the wheel mounts. This gearbox has an offset where the axle tube and diff are located above the centre axis of the wheel, giving

the vehicle great ground clearance.Portal axles also allow the use of bigger

tyres and therefore mean the vehicle can have even more ground clearance. The hub reduction gears also reduce stress on the rest of the drivetrain, allowing for increased gear reduction in the gearbox or transfer box (Marks has kits for that as well) and helping correct speedo errors caused by the bigger tyres.

The portal kits available from Marks, all have a vertical offset of 101mm, or four inches in the old coin. Two portal transmission ratios are available: 1.4:1 and 1.22:1. The 1.22 ratio makes the overall gear reduction seven percent lower than standard when you allow for the 15 percent increase on a rig fitted with 35-inch tyres.

That means overall conversion costs are kept down as diff ratio changes are not really required to achieve normal road speed. This also helps with take-off, where bigger wheels on their own demand a bit more grunt to get away from a standing start easily and quickly.

Fitted with 35-inch tyres, the total

ground clearance is about 150mm (six inches) over standard, or about the same as if you had fitted, or could fit, 43-inch tyres under your vehicle.

Marks’ portal kits increase the axle width (or the vehicle’s track) by 100mm each side. A combination of 25mm or 50mm positive-offset rims, fitted with 35-inch tyres, are used to correct steering geometry. Using these rims also reduces the overall track increase to 100mm or 150mm overall.

The kits use your original standard axles. The front axle assembly, including the diff centre, is completely stripped and cleaned and then fitted with new bearings. The ring and pinion ratios are changed if required and an ARB Air Locker can be fitted at this time if desired. The axle housing is then checked for straightness by Marks’ purpose-built laser alignment tool and straightened if required. Finally, the housing is sealed and sandblasted clean.

The swivel housings are then fitted with new kingpin bearings and a re-machined lower kingpin. A ball joint is fitted under

P

Ground clearance under a standard GU which …

… with portals, literally goes off the scale

Interior view of the cogs

in your reduction hub

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n Nissan Patrol: POAn Toyota LandCruiser: POA

prIce

n Marks 4WD Adaptors, 03 9702 7366, marks4wd.com

coNtAct

the lower kingpin and a strut is fitted to the joint, which is then attached to the main banjo housing.

The front portal is then assembled using all new CV joints, axles, gears, shafts, bearings and seals. Brake rotors are replaced and new bearings and new AVM freewheeling hubs are also fitted. Brake calipers are stripped and cleaned, new seals and pistons are fitted if required and then the calipers and brake pads are attached to the portal housings. New braided brake lines are also fitted at that time. The rear axle goes through much the same process though, of course, not requiring the swivel housing work.

The LandCruiser kits require a bit more hardware and work. This includes a new transmission handbrake (which has got to be better than the standard handbrake found on a Cruiser!) and, up front, new swivel housings. Marks has manufactured these heavy-duty, race-spec, one-piece housing and steering-arm assemblies for a while now and they have proved to be much more reliable in rough, tough conditions.

I’ve driven a few rigs with drop axles over the years. The Malaysian Rainforest Challenge was the most tell-ing experience. There, in a modified shorty Cruiser with portal axles, we went everywhere. The extra ground clearance helped us through deep mud and ruts that would have stopped a rig with normally lifted suspension or even a body-lift.

Side-slope stability can be an issue with portal axles as the centre of gravity of the vehicle has been lifted, but in the Marks 4WD Adaptors case the increase in track helps counter that to a large degree.

But, while there is no doubt that por-tal axles will greatly improve your off-road ability, like many 4X4 mods, such as locking diffs, when you do get bogged, you really are bogged! With portal axles you can get bogged deeper than ever.

I slipped behind the wheel of the Marks GU Nissan running portal axles and, while I didn’t really need to see how it would go in the rough stuff, I was more interested to see how it would handle on the open road.

You truly are in a commanding position

once in the tall cab of the portal-equipped Patrol. Driveability on the blacktop is surprisingly good. Sure, there’s a little more body sway than you’d find on a standard off-the-shelf Patrol, but that is due more to the bigger, taller tyres the rig was running than anything else.

Serious off-roaders and 4X4 competi-tors will find these kits to be a huge advantage to their driving ability and their vehicle’s capability – and you’ll go further in the rough stuff faster and easier. No doubt about that!

Marks’ portal axles are impressive and are, in my opinion, one of the best-value 4X4 accessory kits around. It is incredible what you get for your hard-earned dollar.

Please create logo as per this one, White lettering, yellow X!

New rotors, hubs and

lines are all included

A glimpse inside new Cruiser swivel housing

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