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Discussed below are various topics that relate to traction adding differentials.
The Importance of Traction
Anyone who has watched a vehicle try to climb a slippery slope has noticed that one wheel will begin to slip before the other. Once this happens, the vehicle struggles trying to make it up the slope. The slipping wheel will spin-up and take power away from the other drive wheel. Even on a level area that is slippery, one drive wheel will break traction and spin-up. A soft surface such as snow, mud or sand will cause the spinning wheel to sink itself in deeper and deeper causing the vehicle to get stuck. Aside from the inconvenience and annoyance of getting stuck, safety issues include becoming stranded, risking injury while trying to free the vehicle, and increasing the chance of having an accident.
Bottom line: Greater traction makes the important safety difference in avoiding getting stuck and enjoying better vehicle control when driving.
Traction is also important for outdoor enjoyment and recreation. Whether you want your muscle car to lay two stripes when coming off the line, are trying to get your family to their favorite skiing spot, or are getting ready for a weekend of recreational off-roading, hunting, or fishing, you need traction.
Very poor traction behavior is a characteristic of conventional “open” differentials that are still used today as standard equipment on most vehicles. This century-old technology delivers virtually all the engine power to the wheel that begins to slip first. Because the wheel that begins to slip has the lowest amount of traction and because all the power is delivered to that slipping wheel, there is insufficient power applied to the non-slipping wheel to adequately propel the vehicle. Although open differentials work adequately on ideal driving surfaces, they perform poorly under adverse traction conditions.
Electronic Traction Control
Electronic traction control senses for wheel spin and triggers when detected. It applies braking action to a spinning wheel and holds back the throttle, all in an attempt to propel the vehicle forward. Electronic traction control is usually designed to work in conjunction with the vehicle’s anti-lock braking system (ABS), and is adapted primarily to passenger cars rather than heavier duty vehicles. Even with light duty applications, performance results are inconsistent. Car owners with electronic traction control often learn that their traction improvement is so limited they can’t even climb their driveways after a light snowfall. Many also complain of annoying side effects, such as power pauses when driving normally. Therefore, on/off switches are used with almost all electronic traction control systems. Because of their idiosyncrasies they are usually turned off, providing no automatic traction benefit whatsoever.
4 Wheel Drive
The increasing demand for more traction has made 4×4’s so popular that they continue to be produced in record numbers year after year. But “4 wheel drive” is a misnomer that misleads consumers into believing they have the ultimate traction vehicle. They don’t. Many 4-wheel drive vehicle owners get stuck in situations they believed their vehicles could easily handle. 4×4’s are equipped with the same differentials that have the same shortcomings as those equipped in 2-wheel drive vehicles.
Most 4-wheel drive transfer cases automatically direct engine power to the front axles providing what is referred to as “All-Wheel-Drive” operation. Another misnomer. These transfer cases are, in effect, center differentials that are technically similar to the front and rear differentials. These differentials track the path of least resistance, which unfortunately is the lowest power delivery path. Loss of traction in just one wheel of many of these “full time” 4×4’s and the vehicle will lose available power delivery to the other wheels, thereby running the risk of getting stuck.
Selectable 4-wheel drive center sections will, when engaged, provide better traction than all-wheel drive units. But, they cannot be driven on-highway when engaged due to severe driveline windup that can cause serious breakage or bind-up the driveline so badly that the vehicle will stall. Only after lifting the vehicle to relieve the windup will it be able to be driven further. As a result, most selectable 4-wheel drive vehicles are pre-dominantly driven in basic 2-wheel drive mode. Further, front wheel unlocking hubs are often added to entirely disconnect the front wheels from the front axle. To activate the front wheel drive in these 4×4’s, the center transfer case must be manually engaged and both front wheel hubs physically turned until locked. Disconnecting is equally as difficult.
Few 4×4 owners understand the ramifications of 4-wheel drive operation or comprehend the true price of ownership. It’s an unfortunate reality that performance remains inadequate after spending thousands of dollars more to purchase a 4-wheel drive vehicle and incurring all the associated recurring costs (including much lower gas mileage, accelerated tire wear, added maintenance expenses, higher registration fees, and significant insurance premium increases). 4×4’s can now be upgraded with the Powertrax No-Slip Traction System to achieve the maximum traction performance expected of 4-wheel drive vehicles. 2-wheel drive vehicles can be transformed with the Powertrax® No-Slip Traction System to obtain better traction output than conventional 4 x 4’s.
Limited-slip differentials behave very much like open differentials. Through various forms of friction mechanisms, they transfer a relatively small amount of power to the non-slipping wheel. They are generally smooth and quiet, but as the name implies, performance improvement is limited. Friction clutches reduce gas mileage, degrade under normal driving conditions, easily overheat when slipping and usually wear out rapidly becoming useless. The clutch packs require that friction/silencer additives be added to the differential fluid, which reduces overall lubrication effectiveness. Despite the marginal traction benefits offered by limited-slip/posi differentials, consumers have had little alternative but to accept the limited-slip/posi differential options offered by vehicle manufacturers, for marginal traction improvement, in lieu of conventional open differentials.
Locking differentials, in effect, lock the two drive wheels together — somewhat like “spools” that solidly connect the axles together. When powering straight ahead, engine power is equally delivered to both drive wheels. However, unlike spools that will not differentiate when turning and are therefore not streetable, lockers allow full wheel differentiation when cornering. Unlike the poor traction characteristics of open or limited-slip/posi differentials, when one wheel looses traction, locking differentials deliver engine power, not to the slipping wheel, but to the wheel with the highest amount of traction. Although locking differentials deliver excellent traction output and allow full wheel differentiation when turning, they are notoriously harsh and noisy. Disengagement is abrupt, you can hear a ratcheting noise when cornering depending on the background engine noise, engagement is delayed, and significant backlash (slop) is added to the driveline.
Used primarily in heavy industrial applications, that can be more forgiving than passenger cars or trucks, lockers have been adopted out of necessity by extreme off-road and performance-racing enthusiasts despite their harsh drawbacks. Until the development of the Powertrax® No-Slip Traction System, no better alternative has existed for obtaining high traction results.