Old four-wheel steering systems are fascinating. As a car option, it’s kind of a controversial one. The benefits of 4WS aren’t as easy to articulate as, say, all-wheel-drive, but there are still drivers who swear by it. It wasn’t until very recently (like, the last five years) that four-wheel steering actually got good — that is, they became invisible to customers instead of making the car feel disconcertingly unstable.
Japanese automakers were experimenting as far as back as the 1980s with production cars with Nissan, Mazda, Honda, and basically everyone experimenting with 4WS. Somehow, a version of this technology percolated into GM’s mid-2000s GMT800 SUVs and trucks with a technology called “Quadrasteer.”
Quadrasteer was four-wheel steering applied to a live rear axle. GM applied it to big trucks and SUVs, so instead of cutting down GT-R lap times, it was meant to improve towing and maneuverability for Chevy Suburbans and the like. Everything else up to that point had been an independent suspension setup with several different methods of physically steering the rear wheels. For a few examples, let’s look at the aforementioned Nissan HICAS and a few other similar systems.
HICAS had two distinct iterations of its system, HICAS, and Super-HICAS. Both generally worked the same way with a relatively simple operating principle. Instead of mounting the rear suspension toe arms to a rigid point on the rear subframe like most cars, Nissan replaced those hardpoints with an entire second steering rack at the back of the car.
Original HICAS used a hydraulically powered steering rack and Super-HICAS used an electric motor to turn the wheels. It’s considered an active rear-wheel steering system because the car controls the steering angle based on driver input. Its major drawback is that the rear wheels are linked together by the steering rack, which causes noticeably strange behaviors that can concern drivers. Those strange behaviors are generally a distinct feeling of disconnection from the normally fixed-geometry back axle that most are used to.
Then there was Mazda’s DTSS. Used on the second generation RX-7, known as the FC3S among fans, it actually didn’t use any linkages or steering racks and it is a passive rear-wheel steering system. Mazda kept it simple: engineers designed bushings in the rear hubs to deflect in a predictable way under different levels of cornering load. When loads were low, it would deflect in a way that caused toe-out for more responsive steering. When loads were high, it would then deflect to a toe-in condition to promote cornering stability.
Admittedly, it barely passes as a rear-wheel steering system but it is interesting. Mazda did similar engineering on the third-generation NC Miata and RX-8 where the bushings would deflect a certain way on initial load to cause an alignment change for response and suspension kinematics stepped in under compression to stabilize the car. It’s pretty nifty engineering, even if it causes somewhat non-linear behavior in their sports cars. It was a cool way to independently control each rear wheel as well.
But arguably the best rear-wheel steering system is Porsche’s rear-axle steering, which has benefitted greatly from modern technology. In a strangely roundabout way, it combines the best of both the aforementioned systems: active control and the ability to control wheels separately. Porsche uses individual steering actuators on each rear wheel in place of the toe arms. I just wanted to mention it as the best there is, mainly to help explain how unusual the aforementioned Quadrasteer is.
Unlike anything else I mentioned, this four-wheel steering system is purely for low-speed maneuverability and high-speed stability, as well as towing stability. It was never designed to help a GMT800 Chevy Suburban or GMC Yukon take corners better. It also has that extra twist of being applied to a live rear axle.
Developed by automotive parts and engineering powerhouse Delphi for GM, the system boasted a dramatic amount of steering angle compared to most, if not all, rear-wheel steering systems. Its 15 degrees of maximum steering angle at low speed is evident for the casual observer. I’m willing to bet some folks saw the system in action at their local grocery store and did a double-take or two.
This system seems pretty clever when applied to a larger application like this. Have you ever tried to maneuver a big truck through a tight parking lot? I could always use a little more steering angle and Quadrasteer would do the trick by decreasing turning radii by 21 percent. Trouble is, the option cost $7,000 bundled with other luxury items to start in 2002. Through a series of price drops, it settled down to a mere $1,000 standalone options before being dropped entirely for the 2005 model year thanks to a poor adoption rate.
Of course, those 15 degrees would go the opposite way of the front wheels at low speed and the system would use much less steering angle going the same direction as the front wheels at high speed. In trailer towing mode, it would limit to 12 degrees. The system itself was ingeniously simple: it uses a steering rack powered by an electric motor that uses normal tie rods to turn the rear wheels. The more involved part was modifying the existing Dana 60 live rear axle to have kingpins so it could steer. To my eyes, it looks like a Dana 60 turned into a front axle.
Quadrasteer-equipped trucks are fairly rare and especially difficult to find in the already dense sea of GMT800 trucks on the road. The motoring press hailed the technology as a new horizon for trucks, but that was ultimately wrong for that period. Automotive News reported that 16,000 Quadrasteer trucks were sold through 2005, out of a few million trucks total.
Today, ZF is working on a four-wheel steering system for Ford F-150 pickup trucks and GM is planning to re-introduce four-wheel steering on the far-in-the-future electric Silverado, and GMC is planning a system on the upcoming Hummer EV. With the efficiency and technology that 20 years of automotive development has afforded engineers, there may be a chance for a breakthrough truck-based system yet.
I suspect that this system was exorbitantly expensive in-period. Much of that 4WS innovation we saw in Japan was driven by a historically strong bubble economy and this was pre-recession GM that seems like it did almost whatever it wanted. For sports cars, it solves a problem created by excessive weight and size. For trucks, it manages an already large vehicle and makes it easier to maneuver and tow. I can even imagine negotiating a rutted, foggy, switchback mountain trail with superior agility.
I think that this was an idea that died too soon, for all the wrong reasons. It was a great idea and it might just come back soon. Admittedly, most truck buyers probably aren’t searching for heightened agility (much the opposite) but it would make trucks more accessible and useable in more situations. It also doesn’t seem like Quadrasteer trucks are getting any love or extra value for the weird and useful feature, even for how rare it is.
Pardon me, I’m going to scrub Craigslist and Facebook Marketplace for a clean Suburban Quadrasteer.
