Custom 4x4: Mercedes-AMG LeTech G63

We all love hardcore off-road, trail-smashing brutes, but they can be a pain to drive on regular streets, the family normally hates them and they’re as practical as a flyscreen on a space shuttle. Luxury models from Europe are nice, but they don’t seem to have the same ability off-road. Are we destined to cruel compromise?

Not if German company LeTech has anything to do with it. The shining white G-Class on these pages is one of the demo vehicles out of the now-defunct LeTech USA, an outfit run out of the Bill Rader Motorsports workshop.

LeTech design and manufacture the portal hub conversions used on AMG’s own beastly 6x6 G-Class, but now it has designed a kit that can be used on regular G-Wagens. You’d do this conversion if you wanted to keep the on-road manners of a stock G-series, but with an extra 457mm of ground clearance.

A portal conversion essentially moves the driveshaft to the top of the hub where it drives a reduction gear. It lifts the drive axle away from the centre-line of the wheel and gifts a healthy increase in ground clearance. This saves having a diff or axles hanging low under the car, keeps the original suspension geometry and reduces strain on hubs thanks to the reduction gear.

Portal-driven hubs aren’t new – they’ve been used on military vehicles and some Volkswagens dating back to the 1940s – but they’re serious aftermarket upgrades and the engineering doesn’t come cheap. Unimog portal axle conversions have been popular on competition off-road vehicles for many years, while Marks 4WD in Melbourne uses Aussie know-how and skill to produce its own portals for Patrols and LandCruisers.

Thankfully for LeTech, Bill Rader is no Johnny-Come-Lately to the sport of engineering. Bill has spent years working on transmissions for Porsches and custom-built race cars that compete – and win – in heavy duty events like the Daytona 24 Hour, as well as SCCA, Grand Am, American Le Mans Series and World Challenge.

He knows precision engineering and how to make gear-driven parts survive under high-stress environments. So he’s the perfect guy to build the ultimate dune-hopping, rock-crawling brute that can then back up and be comfortable on a freeway commute or dawdling through the suburbs.

“The axles used in this conversion are the same exact brand Portal axles used by the Mercedes-Benz factory in the G63 6x6,” Rader says. “We have taken the ultra-luxurious, powerful and very off-road capable G63 and given it almost 18 inches of ground clearance – making it one of the best off-road vehicles available, while also giving it a menacing presence on the street.”

As part of the kit, extended wheel arches are included, with a choice of carbon-fibre or fibreglass for their construction and, while the LeTech USA white knight rocks standard G63 bars, the German company has upgrade front and bumpers which include a winch option, as well as a range of side steps and a roof rack with a ladder, too. Not fitted to the G63 were the upgraded bashplates or on-board tyre-inflating system.

The bead-locked wheels span 18x8.5-inches and have been wrapped in Falken WildPeak All-Terrain rubber that measure 37x13.5x18in. LeTech spent time ensuring the G63 would still drive like the well-engineered machine it left the factory as, a fact complicated with the huge suite of electronic safety technologies on board.

“Using the portal axles and the tyres to gain all the lift means the suspension geometry is not changed at all,” Rader explains. “This translates into no change in on-road handling other than the feel of the larger tyres, while the gear ratio inside each of the portals is the exact ratio to compensate for the 37-inch tyres. So all systems work as normal, including the speedometer, ABS, ESP and so on.”

The twin-turbo 5.5-litre AMG V8 engine has been spruced up from the standard 544hp to a monstrous 700hp, thanks to a suite of Brabus upgrades. If AMG is Mercedes’ HSV, then Brabus may as well be the Holden Racing Team.

For decades it has specialised in adding hundreds of horsepower to unsuspecting Merc models with its almost-silly turbocharged V12 and V8 engines. Its twin-turbo 800hp V12 Rocket model is based on the humble CLS, but it has been the fastest four-door car on the planet for 10 years, with the current model exceeding 370km/h!

While plus-200mph Autobahn bombers are its forte, even the G-series can’t escape its attention, with a full range of performance upgrades available for the legendary off-roader. The magic of turbos means most of this comes down to air and fuel management, and a healthy increase in boost.

The stock seven-speeder remains under the LeTech G63, as do many of the electronically controlled suspension components. Stock-standard AMG equipped the G63 with huge six-piston front brakes, and they have remained on the LeTech model.

It’s a bombastic vehicle, but it’s not Bill’s first attempt at building a serious off-road G-Wagen. LeTech USA’s other test vehicle was a fully kitted-out G500 that sported all the bars and rock-ready upgrades. Bill even took it up trails in the Las Vegas area with his local Jeep club, besting many of the kitted-out Chryslers!

But the G63 remains a special beast, even if it is currently for sale. “This is currently the very first and one and only LeTech portal axle G63 in the USA,” Rader says. “A 2014 model, it has under 6000 miles on it, is in perfect condition and is ready to take on any terrain you could throw at it; from malls to mountains this thing will go anywhere, in style.”

The only catch is the price, with Rader requiring US$250,000 (AU$330K approx.) before he signs over the title to the new owner. We might have to compromise a little longer with rough dailies!

Nothin’ but a G-thang

The G-series, or Gelandewagen, has a history dating back 30 years, originating as the answer to a request from the Shah of Iran for a capable off-road vehicle. It has since seen service with the armed forces for most major military powers. The Australian Defence Force has in recent times replaced most of its Land Rovers with G-wagens – even the Pope got in on the action a few years ago with a heavily customised example!

Mercedes-Benz had considered killing off the G-Class in favour of the massive, hyper-luxurious GL-series, but G-class fans are a staunch bunch and made M-B back down. It opened up sales to the USA in 2002 and the G-series scored another win with both off-roaders and Beverly Hills fashionistas alike.

The G55 and G63 AMG models widened the appeal even further, with sports-tuned suspension, brutal V8 engines and performance times that most muscle cars struggle to achieve, yet were still capable off the tar!

Updated and refreshed in 2014, the 1980s styling copped a tweak with new front-end and LED headlights, as well as a full suite of 21st Century electronics and a dashboard design that dates from the Arctic Monkeys era, not Duran Duran.