Pickup Trucks 101: What You Need to Know About Traction

Chevy 2500 G80 Auto Locker Towing 10 000 lbs in snow II

Editor's note: Longtime readers of PickupTrucks.com may remember this series title from several years ago. In the interest in better serving our less experienced readers, we are resurrecting it, discussing some of the more important pickup truck topics. We start with one of the most basic issues — especially when driving on slippery streets with an empty bed — traction.

We'll have more of these back-to-basics articles in the coming months, so stay tuned. And don't be shy about adding your two cents or suggesting topics for discussion in the comments section below the article. If you're not registered to add comments, take a few seconds and do so now. We want to hear what you have to say.

By Matthew Barnes

Have you ever tried to accelerate quickly to merge onto a high-speed highway in bad weather and been stuck spinning one wheel? Open differentials are important when making turns as they allow for the outside tire to move faster than the inside tire; unfortunately, they also allow all the power to go to the wheel with the least amount of traction. In most driving conditions this is fine, but when driving in inclement weather or on rough or muddy terrain, the vehicle can get stuck spinning one tire on a slick spot while the other three have great traction. Hauling or towing a heavy load can make driving in these conditions with an open differential even more difficult.

To combat this, many manufacturers offer some form of traction aid. These range from applying the brakes on the spinning wheel(s) by using the antilock braking system to locking the differential so that both wheels spin at the same speed regardless of what surface the tires are on. Many systems offer a combination such as the Toyota Tacoma, which has active traction control and an electronic locking rear differential.

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Antilock Braking Systems

Many manufacturers offer ABS traction control standard on their pickups and SUVs. Some manufacturers go beyond basic traction control with an off-road version. These types of systems can be found on Toyotas, Nissans, Jeeps, Ford, GMs, Rams and many others. Vehicles with ABS have sensors on each wheel to determine if a wheel is locked when it should be spinning and if the ABS needs to be activated for that wheel. These same sensors and antilock brake systems are used to brake a wheel that is spinning significantly faster than the opposite wheel on the same axle. These systems are inexpensive since they use hardware that is already in place. The downsides to these systems are that they can produce loud grinding sounds, overheat if used too much, and cause extra wear and tear on the brake system. Many can be turned on and off by pushing a button. They are also sensitive to throttle and brake inputs, and have a bit of a learning curve, but once mastered ABS traction can be invaluable.

Limited-Slip Differentials

There are two main types of limited-slip differentials: gear driven and clutch driven. Gear-driven differentials, often referred to as Torsen differentials, use worm screws and worm gears to control the amount of torque being sent to each axle. There is no banging or slamming found in gear-driven limited-slip differentials because they are always engaged. They are also strong and don't require special additives to the gear oil. Gear-driven differentials work on a torque multiplying system. If a differential has a bias ratio of 3:1 it will multiply the torque on the low traction tire by 3 and send that much torque to the high-traction tire. If the wheel with less traction has 40 pounds-feet of torque resistance, then the other side would have 120 pounds-feet of torque transferred to it. The downside to this system is when one tire has no traction the differential can't send torque to the tire with traction because any number times zero equals zero. In many situations, applying the brakes and throttle at the same time will allow enough torque to transfer to the tire with traction to get the vehicle moving again. These types of differentials are commonly used in the rear differentials of trucks and SUVs, the center differentials of all-wheel-drive vehicles and even sometimes in the front differential, such as the desert-running Ford F-150 Raptor.

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Clutch-driven differentials work much like the clutch in a manual transmission, but they use a series of clutch plates to add torque to the wheel with traction. Often they are sensitive to the speed difference between the wheels, meaning the faster one wheel spins in comparison to the other the more torque gets sent to the wheel with traction. These differentials can transfer torque to the wheel with traction even when the opposite wheel has no traction. The downside to clutch-driven differentials is that they wear out with time and need to be rebuilt. They also require friction additives in the gear oil to ensure that they work effectively.

Locking Differentials

There are many types of locking differentials, but they all work by forcing both wheels to spin at the same speed, effectively creating a 50/50 torque split between the wheels. Manufacturers offer two main types of locking differentials: electronic locking and auto locking.

Electronic-locking differentials, or e-lockers, operate by using an electromagnet or a solenoid to engage the locker. These are offered in many Toyota, Ford, Ram and Nissan trucks and SUVs. They are predictable; the driver chooses when to engage or disengage the mechanism, but most can only be engaged when the vehicle is in 4-Low and not while moving. This can cause problems in normal driving conditions where you don't want the differential locked full time, but hit a slick spot and the vehicle is stuck or significantly slowed from spinning one wheel. The Toyota Tacoma and 4Runner; Nissan Frontier; Ford Raptor, F-150, F-250 and F-350 have e-lockers. The venerable Ram 2500 Power Wagon has electronic locking front and rear differentials and a gear-driven limited-slip in the rear.

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Auto-locking differentials are activated when one wheel spins about 100 rpm faster than the other wheel on the same axle. The difference in speed causes a mechanism to activate and lock the axles together. These can engage with a bang and can even cause damage to the axles or differential if the traction difference between the two wheels is high. They work well in most conditions. GM's Eaton G80 used in many of its trucks and SUVs is an example of an auto-locking differential. Auto lockers can engage even if one wheel has zero traction or is lifted off the ground. The downside is that the driver doesn't get to choose when to engage or disengage the locker.

Other types of locking or locked differentials include air, hydraulic, cable, ratcheting and spools. There are even some complicated electric over vacuum over hydraulic systems like the one in the Mercedes-Benz G-Class. Most of these are available as aftermarket options and they all work differently. Air, hydraulic and cable differentials are similar to e-lockers in that drivers can lock and unlock the differential when they want. Ratcheting differentials are always engaged and allow the outside wheel to spin faster than the inside wheel, but neither can spin slower than the ring gear in the differential. Spools eliminate the differential, so they have a 50/50 torque split all the time.

Which Differential Is Best for You?

Each type of traction device has benefits and disadvantages. Each performs differently in different situations, and there isn't a single type that is best for everyone. Driving style, preferred activities, climate and location are important considerations when choosing a traction device. Following is a short description of the types of traction devices generally used in a particular situation. However, what works best for one person may not work for another person in the same situation. Those who rock crawl equip their vehicles with selectable lockers such as an e-locker or an air locker because they offer the most control and predictability in low-traction situations.

Jeep Moab Rear Ratcheting Locker  Front Air Locker II

When driving in muddy, snowy or icy conditions, a limited slip or auto locker is often easier to manage because they only engage when slip is detected. When hauling a heavy load, or pulling a trailer, a gear-driven differential is a good choice because the increased weight on the rear axle can create a greater traction difference between the two wheels. In this situation, clutch-style devices will wear more quickly than if they were lightly loaded, and auto-locking devices will engage harder, also causing greater wear. Spools are only used in special applications since they are difficult to drive on the street in any condition.

Even more important than which traction device or system you have is knowing what you have and how to use it. Locking and limited-slip differentials behave differently. A gear-driven limited slip is different than a clutch-driven limited slip, and an auto locker is different than a selectable locker. The ABS traction aids also have their own "sweet spots" in which they work best. Simply knowing what your pickup has and how to use it in a given situation will allow the truck to continue on its way despite bad weather or rough terrain.

Cars.com photo by Matthew Barnes, Evan Sears

 

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Dakota Stuck  No Traction Aids II

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Comments

This article should be updated to include AWD, as it is showing up on more and more pickups. AWD is superior for driving on rain-slick roads, snowy roads, and roads with patches of ice. As the vast majority of trucks never go extreme off-roading, AWD makes more sense and is now showing up on the higher-end trucks, as well as an option on lower trims of the Ridgeline, and standard on their upper trims. If you want the best on-road traction in a pickup truck, the Ridgeline RTS AWD is a great value.

Until tire makers produce the absolute-grip tire (no spin) then we'll need other ways to quickly respond to unwanted wheel spin.

Nice report, but leaving out AWD...?

Need to talk about traction control also. The pro's and con's. and how it works

I was in a situation in which i had to drive across about 200 yards of deep muddy road. I gunned it to get momentum and all I did was slow down when the wheels started to loose traction, half way thru I was down to a crawl and remembered the traction control button, ( turned it off) and off I went....

Honda makes the best pickup truck. Chevy trucks are trash imo.

@ Jeff S, - Your not the brightest bulb on the porch are you ?

An old trick for off road traction and dealing with ice/snow is to slightly deflate tires.

I was really nervous about AWD until I owned one, worked flawlessly for 10 years.

" but most can only be engaged when the vehicle is in 4-Low."

I wonder what the reasoning is behind this vs also being engaged in 4 Hi.

An old trick for off road traction and dealing with ice/snow is to slightly deflate tires.


Posted by: Red | Jun 8, 2017 11:39:13 AM

To about 15 psi.

I thought LSD needed special friction type fluids.

Honda makes the best pickup truck.

Posted by: Jeff S. | Jun 8, 2017 9:56:07 AM

Thanks, Jeff.

Is thre Ridgeline a truck? I guess that makes my AWD Vibe an SUV....

@Boeingboy: If you go by the true definition of a truck, then the Ridgeline is, by all means, a truck. Go ahead and look it up in the dictionary.

OTOH, if you listen to some so-called "truck enthusiasts", they assume a truck could only be some conglomeration of a body on top of a separate frame, most likely underpinned by a Hotchkiss suspension. Capability has absolutely nothing to do with that assumption.

@longboat et al

Many assume because the Ridgeline is perfect for them and everyone they know that it is perfect for almost everyone.
Trucks, by their existence, are a compromise.
A reg cab 3/4 or 1 ton 4x4 with solid axles at one end, a Ridgeline at the other.

The Ridgeline is a good truck for folks who don't tow much, if at all, don't haul much, and never venture off smooth gradesdort roads. But the AWD system is just that and it rapidly shows weakness in anything remotely technical. The truck itself is low slung and softly sprung for the typical buyer. Nothing wrong with that, but as it has been shown before, when pressed into service the compromises become rapidly apparent.

Conversely, using a HD truck as a commuter is a waste.

But, I need a HD truck. A Ridgeline won't cut it. It can't tow what I can, haul what I can, doesn't have a low range in the transfer case, and most importantly with 5 adult males in the cab it still has plenty of payload capacity for the trailer pin weight.

GMs GovLoc (G80) is terrible. It is weak, grenades frequently, and unlocks at a relatively low speed. So in situations where wheel speed is important, it might as well be a peg-leg.

For good, predictable traction a Torsen up front and a limited slip or electric locker in the rear.

Honda makes the best pickup truck.

Need to talk about traction control also. The pro's and con's. and how it works

Toyota's idea of a Limited Slip Differential is use of the anti-lock breaking system to simulate it, which is prone to overheating the braking system. In reality is nothing more than less invasion traction control.

@James:

I'm not sure you understand just how capable the Ridgeline is as a truck. It tows 5000lbs better than a Tacoma can tow 5000lbs, even though the Taco is rated for more. The payload rating on the Ridgeline is greater than many full-size half-ton trucks that have the same options - don't blindly follow blanket advertising - actually check the sticker on the doorpost.

It has the largest bed of any mid-size four-door, amd you dont have to buy an extra bed-space-wasting toolbox for it because it has one already built-in under the bed. It also has the roomiest cab of the mid-size trucks, along with power AND MPG that are both at the top of its class with just a SINGLE engine configuration.

As for AWD, it will outperform all other trucks on the road in inclement conditions, at least until the snow gets over 14 inches. Yes, an owner has had the 2017 Ridgeline out with 14" snow on the ground, and with winter tires, he reported it was a blast, and "unstoppable". More snow than that, you will probably need a truck with an aftermarket lift anyway. If you do extreme off-roading, or very technical off-roading, the Ridgeline is not for you. It will handle fire trails, logging roads, and deep mud roads just fine, however.

Look, I'm not saying the Ridgeline is for everyone. All I am saying is that it is highly under-rated. I drive full-size half-ton and 3/4-ton trucks at work all day, towing often. I've done this for decades. I've probably driven more trucks and towed more trailers than the majority of people on this forum.

If you don't like the Ridgeline, don't buy it. If you dont think it will meet your needs, dont buy it. There aren't enough of them to go around anyway. All I am asking is that people stop spreading mis-information about it because they don't like it or have mis-perceptions about it and its capabilities. If you don't truly know about it, then don't try to influence/educate other people about it!

Devices are great but you overlook common sense and science...

Proper tires are key, and the ability to air down for hard off-roading and not those fancy 22" dumb rims!

Wheel travel can help also.

Weight distribution is also a huge factor!

The taller the truck off the ground, the more chance of it breaking loose in the rear, especially hard cornering.

I raced my 2005 Tacoma X-Runner not only on parking lots, but on road courses in both dry and wet pavement. I actually won rear-drive class in the pouring rain, beating sports cars and the like on corrected time.

It's all about the tires and proper air pressure, I raced with 18x9.5 ASA's that gave me over 12" wide tire footprint in the rear for my BFG R1's...

I adjusted the suspension to make the rear lower than the front, kinda of like desert racing trucks, not only for hard braking but trying to shift as much weight distribution over to the rear axle and springs...

And you have to know how to drive, that is launch properly, auto tranny's are just plain dumb, but for a manual tranny, know your clutch well by going to the drag strip here or there to practice launching. Have to know how to do it properly on the dry stuff to even think about the wet or snow stuff.

By the way a manual is way better at detecting slippage than an auto tranny! Manual tranny acts like another brake, where in winter driving, rarely have to use the brake's, let the tranny slow down the vehicle, because all to often, the dumb driver panics and hits the brake's, and boom, lost of traction follows!

I lost my Tacoma at 70 mph coming out of turn 5 at Autobahn Country Club road course! Did I panic and hit the brake's and jerk the wheel? Nope! I locked the wheel hard right into the lose of traction and kept the throttle down and smoked the rear tires until I slowed down enough to make my adjustments and finish my lap.

Way to often folks use the throttle, brake and steering wheel with huge adjustments and the like and wonder why they end up in the ditch!

Idiot behind the wheel is more important than gadgets!

Honda makes the best pickup truck. Chevy trucks are trash imo.

An old trick for off road traction and dealing with ice/snow is to slightly deflate tires.

The Tundras brake based system was by far the weakest part of the truck.
I have a 2 wheel drive long box. When pulling away in snow it often applies braking to both spinning wheels! Really exiting when pulling on to a highway.



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