Review: POWERTRAX No-Slip Traction System
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Authoring and Photography By: Chris Perosi
Diagrams Supplied By: POWERTRAX, Inc.
First Published: March 2000

Review: POWERTRAX No-Slip Traction System

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The new No-Slip Traction System from POWERTRAX.


Contrary to the absence of the word in the name, the No-Slip Traction System from POWERTRAX is, in fact, a locker. Specifically, it is an automatic locker which requires no user intervention to work properly. There are several advantages to this particular unit over more traditional "drop-in" lockers, however. It is touted as smooth and quiet, even when installed behind a powerful engine and 5-speed transmission. It also reuses many popular factory LSD cases, thereby eliminating the need to reset backlash and pinion depth when upgrading from a factory limited-slip to a locker. Best of all, it can be installed by just about anyone in a few hours in the driveway, using only basic hand tools.

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Exploded View of all the internal parts of the No-Slip Traction System.
Click to Enlarge
Illustration of No-Slip Traction System versus open and limited slip differentials.
Click to Enlarge

How It Works

As illustrated above, the No-Slip Traction System works like many other lockers on the market today: simply put, it puts maximum traction where you need it most. From a driver's standpoint, that's about all you really need to know. But the technical-savvy may wish to know a bit more. The No-Slip replaces the spider and side gears inside the differential, as well as any friction clutches and thrust washers that may accompany them. With the No-Slip installed, the high-strength Zytanium replacement pinion shaft transfers power to the "drivers". The drivers engage the couplers via "saddle springs" which push the drivers away from the pinion shaft. The saddle springs compress to keep tension between the pinion shaft and the drivers until a positive power transfer angle is achieved. This allows full power to be transferred through both wheels when the vehicle is driven straight.

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The No-Slip locker installed in the Dana 44 Trac-Lok case.

While turning, differentiation between the wheels is achieved by the outside wheel accelerating past the inside wheel. This advances the coupler, relaxing the power sent to the outside wheel. As it continues to advance, it is ramped out and disengages from the driver. A synchro ring then prevents the coupler from re-engaging until the turn is complete and the vehicle is once again driven straight. All of this is described in far more detail in the owner's manual.

The owner's manual also goes into great detail warning of some of the negative effects of installing a locker in your vehicle. Driving characteristics will change and will require some getting used to after installation. Some torque transfer may be felt when going from drive to coast and back, and there may be some degree of understeer. Additionally, driveline backlash may increase, due to the locker's built-in backlash.

Street Manners

Our test unit was installed in the Dana 44 rear axle of a 1998 Isuzu Amigo, originally equipped with the Trac-Lok LSD. This particular vehicle puts out 205 horsepower and 214 ft-lbs of torque, and is equipped with a 5-speed transmission, so it would normally be considered a major trade-off to swap out the factory LSD in favor of a locker. Automatic lockers are notoriously noisy, clunky, and harsh when installed on vehicles of this configuration, especially if they are used as daily drivers. However, this is not a traditional locker. Although it shares some of the standard locker mannerisms with other units, the most noise we've heard from it is chirping tires and an occasional soft "thunk" from driveline backlash. No clicking, clanging or banging, not even on initial installation while testing it by hand with the differential cover off.

As described in the owner's manual, some torque transfer is noted as you get on and off the throttle and the torque is transferred from both tires to one, and back. This is especially true while turning, although careful modulation of the throttle can all but eliminate any traces of this. Moderation on the throttle is helpful in other areas, as well, particularly when pulling out from a stop and making a tight turn, as you would pulling out into traffic. Smooth throttle operation will help avoid any tire chirping you might get in a particularly tight turn.

A bit of understeer can be felt in certain situations, particularly on a winding road or a highway exit ramp, where a turn may be taken while still under moderate-to-full throttle. If the throttle is not relaxed or is re-applied quickly during a turn, the two rear wheels will both get power and will attempt to push the vehicle straight. A slight steering correction will be required -- this takes some getting used to, but again, careful throttle modulation can practically eliminate it if you so desire.

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Off the Beaten Path

In extensive trail testing, the No-Slip more than proved its worth in many situations. Our Amigo was easily able to conquer obstacles it had failed to complete before, or where the driver had previously opted to take a bypass. Off-camber climbs, boulder fields, and twisty crevices were gobbled up and spit out the exhaust.

With more than one spotter assigned to keep an eye out for slippage, all reported back that not a single time did the No-Slip unlock, even briefly, while the Amigo was attempting to complete an obstacle. As promised, full, 100% lockup, automatically, all the time when under power on the trail. This simple fact did wonders for climbing, pulling, and clawing abilities.

An odd side-effect of installing a locker is that most rigs will see the benefit of some additional flex in their suspension. This held true in the case of our Amigo as well. In all but the kings of flex, the addition of a locker will force the suspension to flex to its limits, because the vehicle will continue moving even after a tire has lifted. This forces more weight onto the compressed tires, which generally pushes them to compress even further, returning the lifted wheel to the ground. Vehicles who already take advantage of every ounce of suspension movement won't see this benefit -- but the other 95% of four wheelers out there will. In our testing, we were unable to lift a tire in any of the usual "articulation photo opportunity" spots along the trail.

Although it may not sound like it, there are limitations to any locker, and the No-Slip is no exception. On the trail, having two wheels turning with full power on the rear axle causes a tendency to push the vehicle straight, just like on the street. However, on the trail in low-traction conditions, the front wheels can more easily slide straight forward, regardless which way they are turned. This fact must be taken into consideration anytime precise maneuvering is required.

We were lucky enough to be able to perform our testing in an area which had some snow-covered trails, which made for a perfect proving ground for the great equalizer: snow. As predicted, our Isuzu had difficulties climbing one or two snowy and ice-covered hills due to the tendency of the rear wheels to cause a sideways slide. In the same situations, the accompanying vehicles with open and limited-slip differentials had fewer difficulties. Of course, with less throttle and more momentum, this problem could be avoided.


In retrospect, this locker lived up to all of its promises and more. Truth be told, the owner's manual promises that it will be more noticeable on the road than it has proven to be, so that's a good promise to not quite live up to. It's a good compliment to any daily driver setup, where street performance matters, yet it would do the job in any hard-core trail rig just as well. The No-Slip has a high value-to-dollar ratio, given the advantages and the relatively low cost. Any disadvantages are easily overcome by proficient work with the throttle, and the fact that it can be installed by anyone in a few hours, in particular, inside a limited-slip carrier, is truly a value-add.

Installing the POWERTRAX No-Slip Traction System
Installing the new POWERTRAX No-Slip Traction System in a Dana 44 rear axle. This installation takes into account the removal of the carrier and ring gear due to a very low axle ratio, as well as installation inside the Trac-Lok LSD carrier.
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