Tom Wilson
April 1, 2002
Compact and relatively affordable, the Powertrax No-Slip Traction System differential delivers a shark-bite grip. It can be ordered to work with 28- or 31-spline axles. Installation does not require removal of the ring-and-pinion from the differential.

Horse Sense: When first installed, the Powertrax No-Slip Traction System is one noisy, clanking son-of-a-gun, but the metal-shop noises from our differential were hugely diminished after just 100 miles of driving. A light but noticeable clack while cranking around parking lots is the definitive No-Slip Traction System noise. Otherwise, it's basically silent.

It's doubtful if any of us need help initiating a tach-twisting bench-racing session, but if you do, bring up the subject of lockers, limited slips, Traction-Loks, and all that. After all, making twin black stripes on the pavement is something the stock Mustang doesn't do all that well, and the after-market help in this area comes from all points on the mechanical and fiscal compasses.

One of the latest traction aids to hit the 8.8-inch differential is the Powertrax No-Slip Traction System. An all-steel, mechanical-locking device, the No-Slip Traction System falls into the middle of the obtainable area of the "limited-slip" spectrum at $400. It also allows a relatively easy installation-and we will qualify that overused term in a moment-because it does not require upsetting the differential's ring-and-pinion gear relationship. That means there's no backlash to adjust, no dial indicators to use, just a straight-forward wrench-and-screwdriver session. Furthermore, Powertrax positions its unit as something almost revolutionary in two-wheel-drive traction enhancement-the-noisy-as-a-blacksmith-but-absolutely-will-not-spin drive provided by a locker coupled with the less-effective, but smooth, quiet operation of a more traditional clutch-pack (Traction-Lok) or cone-type (Auburn) limited slip.

To find out for ourselves, we went to DriveTrain Direct in Corona, California. There the expert installers whipped a Powertrax No-Slip Traction System into our own '96 4.6 GT-and incidentally rebuilt our tired 8.8-inch axle when they discovered the axles were nicked, the bearings tired, the pinion seal gushing lube, and the preload gone in the gear set-can't say this car hasn't been tested.

At left is the Powertrax No-Slip Traction System driver. At right is one of the couplers that mates with the axle using the splines visible at its center. Note how the driver teeth couple both with the outer teeth on the coupler and the inner set of teeth that are part of the synchronizing mechanism.

The installation is covered in the photos and captions, but here we'll note the job goes basically as advertised. The mechanically adept enthusiast can make this a driveway install, as no special tools are required, but the job is made considerably easier with a hoist as it all takes place at periscope depth. Let us also advise the home installer to study the excellently produced and thorough instructions at length while at the comfort of the kitchen table, No-Slip Traction System in hand. A deceptively simple-looking device, the unit must be assembled in the rear axlehousing. Like a good wooden puzzle, once you understand the details it goes together easily enough, but if approached in a rush it is certain to frustrate-possibly in a major way. That said, the install highlights are to remove the rear wheels, brakes, and differential cover, pull the C-clips, and remove the axles. The differential spider (side) gears or Traction-Lok are removed. The Powertrax system is assembled piece by piece in the differ-ential carrier. Then the axles and so on, go back in.

If you wish, either stock 28-spline or stronger 31-spline No-Slip Traction Systems are available. Thus, if you are like us and desire an axle upgrade, now's the time. Don't forget the axle bearings and oil seals if they are worn, but there is no requirement to change these items for a simple Powertrax install.

What are the peculiarities of driving the No-Slip Traction System? Well, it positively locks the axles together, of that there is no doubt. Punch it hard and the system grabs the axles together, and both tires spin if you have enough steam on line. You can even make a 90-degree turn from a dead stop, spinning both tires all the way. Traction is remarkably improved, and on loose surfaces the improvement is dramatic. In short, the traction improvement is right up there with what a spool or locker delivers. Straightline enthusiasts, especially those wanting a streetable traction solution, ought to be greatly pleased.

Here we're lifting the active spacer from the middle of the driver. This illustrates how the active spacer is free to rotate relative to the driver, and thus block mating of the driver and coupler when axle and driveshaft speeds are not synchronized. When the larger tab on the active spacer slips into its corresponding slot on the coupler, spring pressure joins the coupler and driver together.

Hard-charging cornering enthusiasts have more issues. The traction is definitely there on corner exit, and most of the time the No-Slip Traction System stays locked. However, in higher-speed bends, lifting off the throttle can unlock the unit, and getting back on the throttle then re-locks the differential with a thunk. On the street, this is mainly a nuisance, but on a road course it could be upsetting. We didn't have a chance totry the system on track, but on-off-on throttle applications are definitely affected with a small steering change, which under the most extreme high-speed sweepers would definitely not be welcome. Getting back on the throttle in mid-turn after braking into that turn also results in a thunk and slight steering input. When engaged, the system promotes understeer; disengaged it is neutral, allowing whatever chassis dynamics are built into the chassis.

That brings us to street driving, where the No-Slip Traction System certainly works, but with a few side effects. While turning tightly at light throttle, typically in a parking lot, the system ratchets in and out of lockup, clicking or clacking all the while. Disengaging the clutch greatly reduces this annoyance to the point where, while you wouldn't want such noise coming from a Town Car while pulling up to a parking valet, it is just part of the hot-rod tone on a serious Mustang.

Naturally, there's the occasional thunk and hesitation, especially when starting off from rest. This condition is interesting. Whenever the No-Slip Traction System is open-such as after backing out of a parking place-the car starts off from a dead stop feeling normal, then about a quarter second later the differential clunks into lockup and there is a renewed sense of traction and acceleration.

This is the driver and one couple joined together. The large slot in the side of the driver is where the axle C-clip goes in. This view also illustrates the tough, relatively square-edged dog teeth used to connect the axles to the differential. The ramp angle on the coast and drive sides of these gears is different to allow coupling and uncoupling of the axles.

All that said, there is a neat fun factor provided by this system. It puts a tenacious grip into the rear tires that's a joy to explore. For the hot street and street/strip crowd, the Powertrax No-Slip Traction System provides an affordable, durable, and definitely hard-working traction aid. It is a viable option compared to more traditional but less effective and durable limited slips.

Let's begin by saying Powertrax offers good literature on how its unit-and others-work. In our limited space here, we'll explain the basics so you can better understand what it's like to drive a Powertrax No-Slip Traction System-assisted Mustang.

Key to the No-Slip Traction System is the pair of square-toothed gears attached to each axle. These teeth are held together with relatively small coil springs. Also important are blocking rings that synchronize the meshing of the gears.

In a straight line, spring pressure keeps the dog teeth engaged, the differential is locked together, and both axles receive equal power. The cut of the drive-side of the square teeth in the Powertrax system naturally tends to keep the axles locked together, so keeping the power flowing with your right foot further helps lock the axles together.

When turning, the No-Slip Traction System will keep the axles locked together if you have power on. Just how much power it takes to keep the system locked depends on how tight the turn is. The deciding factor is the slight ramp angle cut into the coast-side of the system's teeth. At some point, the different axle speeds have enough energy to pop the gears apart, and then the blocking rings hold the teeth apart until the axle speeds synchronize again. Thus, driven aggressively, the No-Slip Traction System tends to stay locked; pussyfooting around allows easy turning via open differential action.

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