Smoky burnouts with a pickup's right rear tire roasting in a fog of sizzling rubber are a lot of fun-that is, until someone gets beat. All the horsepower in the world will not do a truck any good if it can't hook up. By nature, even stock pickups with open differentials have a hard time leaving the line quick without breaking the drive wheel loose. In the instance of customized pickups with hot motors pumping out up to four times the original horsepower rating, one tire trying to get things moving is near impossible
Such was the case with John Barkley's '74 Chevy short step powered by a 355-inch small-block packing 440 horsepower. The traction problem with his '74 was severe enough it would rear its ugly head any time he tapped the gas pedal to pull out into traffic or accelerate onto the freeway. The additional hidden inconveniences of poor traction are accelerated tire wear and increased fuel consumption. While some performance improvements are hard to quantify if they can't be measured on a dyno, the installation of Auburn Gear's limited slip differential is easily confirmed on the real dyno-the street.
Before Mike and his helpers, Manuel and Kendall, at Toy Shop Transmissions in Pomona, California, installed the Auburn Gear LSD, Mike suggested we pull the '74 out into the street to observe firsthand just how bad of a problem we were dealing with. As expected, the Chevy laid down one pure black patch of rubber from the right rear tire all the way down the street. Admittedly, it was pretty fun to watch the '74 light up the rear tire, but the real fun would be when we were able to see just how much of an improvement the Auburn Gear LSD would make.
We learned of Toy Shop Transmissions from our friends at Street Rodder, Custom Classic Trucks' sister publication. Nearly 15 years ago in the September '92 issue of Street Rodder, Mike walked readers through installing a kit he developed to eliminate the need for a computer to control a GM 700-R4 automatic overdrive transmission. (In an upcoming edition of CCT we'll install one of Mike's kits into a 700-R4 hooked to a 454-powered '75 Fleetside gasser).
The best way to accurately gauge the effectiveness of any performance modification is to make one change at a time. Using Barkley's '74 Chevy as a test bed provided us with the perfect platform. We retained the 3.73.1 gears, implementing the Auburn Gear LSD as the only modification.
Not having to swap out the ring-and-pinion gear eliminated a few extra hours of labor, leveled the playing field for our comparison test, and best of all, greatly decreased the skill level required for a "do-it-yourselfer" to tackle this job in their own garage (close attention must be paid to reestablishing existing backlash).
 Mike tested the stock Chevy...  Mike tested the stock Chevy 12-bolt rearend without the limited slip. As expected with power going to the right rear wheel only, John's '74 Chevy burned a one-track patch all the way down the street. |  Here are the parts we needed...  Here are the parts we needed for JB's '74 to go from pulling one tire to two. An Auburn Gear LSD with friction additive, new Timken bearings, and a chrome differential cover are thrown in for good measure. |  Mike raised the truck on the...  Mike raised the truck on the lift to access the 12-bolt differential cover. |