Is it a locker, is it a posi? Hum, I would have to say it falls somewhere in between. The manufacturer, Tractech calls it a limited slip differential. The TrueTrac is a gear driven traction adding device. According to Tractech, it provides a controlled amount of resistance to a one-wheel spinout, so that the other wheel (with traction) receives sufficient power to keep the vehicle moving. Sounds easy enough, but does it work? Yes, it does, but there are some control variables to add into the equation. It does not work if one wheel is completely off the ground and has no force acting against it. Enter the first variable, if you provide light break pressure, (i.e.: resistance) during one-wheel up maneuvers, it locks up seamlessly. If you are blasting through a deep mud bog and one wheel begins to spin faster than the other, the TrueTrac will still provide power to the slower spinning wheel provided it still has some resistance acting against it. Sounds a little strange doesn’t it?
Well, the simple fact is that it works. We installed a Detroit TrueTrac in the front our project Jeep CJ-5 and put it to the test in Moab, Utah during the Easter Jeep Safari. The only drawback we found was that it was sometimes awkward to apply brake pressure during uphill climbs, since our Jeep is a 4 speed. This amazing clutch, gas, brake pedal feat was made possible by the ultra low gearing of the T-18 transmission and 4.56 axle gears and a 3:1 t-case gear set from TeraLow. This allowed us to let out the clutch, and apply light brake pressure without stalling the motor. Oh yeah, this Jeep is also fuel injected. I would have to say the perfect application for the TrueTrac is in the front end of any vehicle with an automatic transmission. Our application requires a good bit of driving finesse! With an automatic transmission, you can modulate the brakes and gas pedal to keep the TrueTrac locked up at all times.
Now it sounds like all of this is a bit of a pain in butt, well there is one huge bonus the TrueTrac has over a locker in the front end. A locker in the front axle will cause the tires to push during tight turns on the trail and sometimes require you to unlock one hub just to negotiate a turn. The TrueTrac is almost undetectable during turns with the hubs locked in. You get no feedback or binding from the front end, and still get added traction. The TrueTrac is also not as violent as a locker when engaged; it will not force a tire that is wedged on a rock to continue to turn until something breaks. Since it can “slip” somewhat, it will keep front axle and u-joint breakage to a minimum.
So what is it? It is a limited slip that falls somewhere between a good posi and a true locker. If you don’t do enough hardcore rock crawling to justify a full locker, but need a powerhouse of a traction-aiding device, then the Detroit True Trac is for you.