You Could Once Buy A Chevy Silverado With Four Wheel Steering More Extreme Than The Tesla Cybertruck’s. Here’s How It Worked

It’s safe to say that 1980s nostalgia is still going strong, and one piece of automotive tech popular towards the end of that decade is experiencing a renaissance. Four-wheel-steering may have made its debut on the 1985 Nissan Skyline, spread throughout the industry as a curiosity, and vanished, but now it’s back in everything from sports cars to pickup trucks. Porsches have had it for years, the Tesla Cybertruck famously has four-wheel-steering, as does the GMC Hummer EV, as will the Chevrolet Silverado EV. However, four-wheel-steering on pickup trucks is older than you’d expect. Arguably the best four-wheel-steering setup on a pickup truck went on sale 22 years ago, and while it worked incredibly well, it was a colossal sales failure. I’m talking about Quadrasteer, the holy grail of GM truck tech.

If you’ve never heard of Quadrasteer, you aren’t alone. See, General Motors has always been an innovative company, it just hasn’t always known what to do with its innovations. The electronic trip computer, pioneered by the 1978 Cadillac Seville, quickly spread throughout the industry. The cathode ray touchscreen in the 1986 Buick Riviera? Not so much. Quadrasteer, available from 2002 to 2005 on half-ton and three-quarter-ton Chevrolet and GMC pickup trucks and long-wheelbase full-size SUVs, falls firmly in the latter camp. Oh, and it’s not on an independent rear suspension setup, making it an outlier among four-wheel-steering systems on production pickup trucks.

In short, there’s an electric power steering rack built into the rear differential cover:

How did GM make the ends of a leaf-sprung solid axle rotate around z axes? The same way Jeep makes the current Wrangler’s solid front axle steer — by adding steering knuckles and ball joints.

As for how power gets sent to steer-able wheels, well, the axle shafts have constant velocity joints just like your front-wheel drive car does:

Here’s a nice diagram of the system (with a few bits removed for clarity):

 

As you’d expect from a steered axle, toe was controlled by tie rods, each connected to a knuckle at one end and the diff cover-mounted rack at the other (you can see the tie rods labeled in the yellow and gray image a few pictures up).

But instead of a splined input shaft hooked to an intermediate shaft that you turn with your steering wheel, this steering rack featured an electric motor with a planetary gearset to multiply torque, and a pinion gear to act on the rack. By varying the position of the motor, GM could vary the rear wheel steering entirely electronically. Yep, it’s steer-by-wire back there.

The steer-by-wire rear axle was controlled by a Delphi-engineered module tucked underneath the bed that took input from the steering angle sensor (which measures the angle the driver has the steering wheel pointed), the vehicle speed sensor (measures how fast the truck is going), an insanely expensive rear steering rack-mounted rear wheel position sensor (which is basically the rear steering angle sensor) with splines to connect to the motor, a dashboard-mounted mode switch, and a serial data line. It also accepted yaw sensor input on early examples, but that was phased out for 2004.

In the grand scheme of things, that Delphi module doesn’t use a ton of inputs, but that makes sense when you consider how Quadrasteer had fairly simple logic that went as follows:

• Below 45 mph, the rear wheels would turn in the opposite direction of the fronts.
• At 45 mph, the Quadrasteer system would be in a transitory, neutral state, and the truck would drive like normal. Coincidentally, this was also the failsafe mode for the system, fulfilled using a shorting relay.
• Above 45 mph, the rear wheels would turn in the same direction as the front wheels.
• In reverse or park, rear-wheel-steering is limited to 5 degrees.

Thanks to huge rear wheel wells and little encumbrance, the rear wheels on a Quadrasteer truck could turn up to 12 degrees — two degrees more than Tesla claims the Cybertruck will be able to do with a promised eventual software update, and nine degrees more than what they Cybertruck is currently capable of. Maximum steering angle only kicked in at or below seven mph, which sounds like a limitation but works perfectly in parking lots.

Oh, and maximum rear steering angle was absolutely enormous by rear-wheel steering standards. With the rear wheels turned 12 degrees in the opposite direction to the front wheels, the turning circle of a half-ton pickup truck would shrink down to just 37.4 feet. That’s circle, not radius. General Motors loved to brag about how a GMT800 with Quadrasteer had the same turning circle as a Saturn S-series sedan because it was 1) Amazing, and 2) True.

While towing a 7000-pound camper trailer at 60 mph in two-wheel-steer mode, we were instructed by Lorraine Babiar, the Sierra assistant brand manager, to do something that was farthest from our minds at the moment: Make a lane-change maneuver. We obliged, and as expected, jerking the steering wheel hard to the left and then to the right sent the trailer wagging so violently that we were sure the next stop on the itinerary was the nearby ditch. Somehow we stayed on the road. Next we performed the same test with Quadrasteer in the four-wheel-steer tow mode, and the trailer obediently followed the truck without any dangerous oscillations. With the trailer unhitched, we didn’t detect any twitchy behavior, either. Very neat.

So, not only did Quadrasteer make a half-ton GM truck easier to maneuver in tight spaces, it also made it safer while towing. Talk about killing two birds with one stone. With Quadrasteer, General Motors had finally made the USDA Prime half-ton truck work just about everywhere, so can you guess what happened? Yep, nobody bought it.

Oh, but it’s easy to see why. In GM’s hubris, the inaugural 2002 year of Quadrasteer saw the option bundled into a $7,000 package. I repeat, $7,000 in 2002 money. If you walked onto a Daewoo lot at the end of a month in 2002, you probably could’ve rolled off the lot in an entire ex-demonstrator Lanos for $7,000. Is Quadrasteer cooler than a Daewoo Lanos? Nobody’s ever made that comparison before, but it all depends on whether or not you’ve seen Pineapple Express.

For 2003, GM’s accountants separated Quadrasteer as an option with Mr. Trailer reporting that the price of adding Quadrasteer stood at $4,995 in 2003. That wasn’t enough, so the bean counters went into price-slashing mode and dropped the cost of the option to just $1,995 in 2004. It was too late, though. Dealers who couldn’t shift expensive Quadrasteer-equipped ’03s likely didn’t have much of a reason to stock Quadrasteer-equipped ’04s, so this nifty technology became a case of “if you know, you know.” By the end of 2005, GM had pulled the plug, and four-wheel-steering on a pickup truck was dead until the latest wave of electric haulers.

Total production? About 20,000 trucks and SUVs with Quadrasteer. While that would be wildly successful if we were talking about a Lotus or a car made entirely of peanut butter, we’re talking about half-ton GM trucks and SUVs, the heartbeat of America, baby. Forget by-the-truckload, these trucks sold by the trainload, and 20,000 is a drop in the bucket.

General Motors can take as much credit for implementing it as blame for killing it. If Quadrasteer were cheaper, it could’ve caught on. American consumers are generally price-sensitive, and if they’ve done fine without newfangled technology for decades, they might just turn up their noses if said tech is too expensive. Still, we love that Quadrasteer exists, and we love that a dedicated cadre of enthusiasts is keeping the legend alive today, by maintaining and enjoying their Quadrasteer trucks.

Oh, and if you’re looking to quickly spot a GMC Sierra, Chevrolet Silverado, GMC Yukon XL, or Chevrolet Suburban with Quadrasteer in the wild, the easiest tell-tale is a set of flared rear fenders with clearance lights. Due to needing extra room for the rear wheels to turn, GM installed wider rear fenders on trucks (flares on SUVs) that added two inches to the width of a half-ton GM truck, pushing it over the legal threshold for vehicles without clearance lights. The more you know.

(Photo credits: GM, eBay sellers)

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