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Dynatrac build an aftermarket kit for Jeep models or can be made to fit other vehicles.
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As you can see, the centre of the axle sits much higher than the centre of the hub.
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In the case of the AMG 6x6, additional support brackets help strengthen the axles.
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It’s easy to see why so many people like the added clearances Portals provide.
Words and photos by Budd Stanley, additional photos courtesy of Jeep, Mercedes and Dynatrac
If you are new to the off-road world you have probably heard the term Portal axles bantered around club circles. But what are Portal axles and why should you care? Truth be told, they are incredibly useful things, however they come with some negative characteristics as well. So to shed a little light on these popular modifications for aggressive 4WD’s, we take a look at the not so new concept of Portal axles.
The Rundown
On any vehicle equipped with a solid axle, the lowest point, whether the truck is lifted or not, is the differential yoke. The first modification anyone makes to a 4WD is to install larger tires. This does provide you with better grip off-road with the correct tread pattern; however, the biggest reason for bigger tires is that it is the only way to lift the differential yoke up higher. You can mount any suspension and body lift kit in the world that you want; yet the yoke is still only as high off the ground as the height of your tires.
So what are Portals? Well, quite simply, they are a solid axle system that has the differential yoke placed well above the axles centre line. From the differential, the axles run out to the wheels like any other solid case. However, instead of running through a bearing and on to the hub, the axle connects to a gearbox that utilizes a drive gear, two idler gears, and a large driven gear that directs drive down to hub units, which are much lower than the case. In most cases, five to six inches lower. This means the hubs are mounted lower, increasing the ground clearance of the axle itself. It is an incredibly useful feature to have in a 4WD vehicle that see’s aggressive terrain; but there are a few considerations to understand before purchasing them
The Good
There is a reason why just about anyone who puts larger, more aggressive tires on their 4WD lusts after Portal axles. In short, they are the ultimate off-road modification you can make to your rig, doing away with the weakest link when it comes to ground clearance. Not only do Portals enhance clearance on a rig, they are, for the most part, very rugged and reliable in adverse conditions. Many use military style units; these are designed to keep people alive in combat situations and are more than adequate for navigating the most aggressive trails, or even forging new ones.
The Bad
First of all, these bloody things are heavy, and they are heavy in a bad way. 4WD’s already have a massive amount of unsprung weight. Unsprung weight is the weight of all the components on a vehicle not being held up by the suspension, like for instance the wheels, brakes and axles. The more weight, the more this mass responds to movements and forces on its own, eliminating the effects of proper suspension tuning. They are also not known for their on-road performance and many are only good for a top speed of 100kmh, if that. So if your 4WD is a daily driver, Portals may not be for you.
Of course, bolting up a Portal axle under your rig is never going to be a painless affair. While there are dedicated bolt in axles designed to fit popular 4WD’s, the cheaper way is to get a set of Portals off a Unimog or some other manic military vehicle. This route will require a heavy amount of fabrication to make the axles fit within the vehicle specifications as well as to keep proper suspension geometry.
Portals have more parts, which means they require more maintenance, as you would expect. Along with the differential, there are oil reservoirs required for both portals. Ideally, you will need to replace the oil in all three reservoirs every 8,000 km.
The Ugly
Of course, anything this extreme costs big boy money, and in the case of Mopar Portals, expect to dump at least $12,500 on a single axle. Double that with the two needed and you have a fair chunk of change that really can be better used on all manner of off-road modifications, which will likely yield better results per buck than some really cool and complex axles. There is also the option of getting used units off a Unimog or similar military vehicle for around $3000.
While Portals are magnificent things that massively increase the clearance of anything they are mounted too, they are also not for everyone. Now that you have a little more information about what Portals are, you can choose for yourself, if Portals are worth the price.