Before we started the install,...
Before we started the install, we wanted to see just how inadequate the stock open differential was. We placed the right wheel and tire on a zero-traction roller device and strapped the axle to a pole with a scale that measures pulling force between them. The wheel with no traction spun and the one on the ground didn't do much at all. When we were done, the scale had recorded only about 20 pounds of pulling force. There's definite room for improvement.
We all love horsepower, but having a lot of it isn't going to be much good if you can't get it to the ground. Common sense tells us that the best way to do this is to get as much power transferred through the tires to the ground as possible, and to do this both tires need to be utilized. Once both tires are spinning, then we can play with bigger and stickier tires and other suspension mods to help plant them better. Another situation where having reliable power transfer is important-that those of us in the fair-weather states forget about-is in adverse weather conditions when one tire might be affected by snow or ice. Horsepower and torque are not big factors here.
A large percentage of cars are running around with an open differential that provides engine power to the wheel with the least amount of resistance or traction. This means that the wheel that's spinning gets the power-we'll demonstrate this later. The cure for this is usually to install some kind of posi or limited-slip unit, but in most cases this requires special tools and knowledge that most of us don't have to set the rearend up properly. A few years ago Powertrax developed a traction solution called the Lock-Right Locker which can be easily installed in less than a couple of hours with no special tools.
The Lock-Right worked on the street but had been developed with off-road as the primary use. As a result it had a light clicking noise that could be heard when turning during normal cruising which many people didn't want for their street cars. To solve this and to take care of the street guys Powertrax recently introduced a new unit called the No-Slip Traction System which provides the maximum traction of a locking differential combined with the smooth and quiet operation of a limited-slip device. A precise synchronization mechanism eliminates the ratcheting sounds typical of other locking differentials, and a special gear-and-spring design reduces the backlash. Units are available for just about any mainstream vehicle and cost around $400.
The Powertrax No-Slip unit...
The Powertrax No-Slip unit is very compact and comes out-of-the-box assembled, as seen here, with step-by-step, model-specific instructions provided with every kit. The installation is simple because no ring-and-pinion set-up is required, and in most cases a wrench and screwdriver are all you need.
Continuing on our foundation building for our '70 Monte Carlo, we contacted the folks at Powertrax and went through an installation with one of its engineers, Valentine Cucu. The installation is so easy and quick we had to have Cucu slow down so we could take our pictures. But even with his pausing for photos, the time it took from when the Monte Carlo was lifted up on the hoist to when the rearend was filled back up with differential fluid was less than 40 minutes.
At the time this is being written we have had a couple of weeks and about 600 miles with the No-Slip unit and have found it to perform very well. The car pulls around corners much better thanks to better power transfer and seems to handle better. The unit is noticeable, however, while performing slow maneuvers such as parking we can hear a light click as it disengages, but this is generally with the radio off and the window rolled down. There is also a little bit more back lash than the original open differential when shifting between Reverse and Drive, but other than that the unit is quiet while cruising and seamless in its operation. One thing to note with the installation is that the use of the grease to help hold the unit together will make the unit disengage hard for the first 100 miles or so until the grease is dissolved and the parts seat during the break-in period.