Building a heavy-duty rearend for your Mopar used to mean either buying a Sure Grip 8 3/4 or going for the famed Dana 60. Often, due to cost or availability, neither is realistic. Fortunately, there is a low-buck solution to maximizing rearend traction.

We contacted National Drivetrain and uncovered all the hardware needed to turn our open differential into a genuine locker without breaking the bank.

A locker? That's right. National Drivetrain has the parts you need to give your red light brawler all the traction it craves.

Our axle assembly featured a 741 casing (which we upgraded to a 742 during the course of this buildup) with an open differential and 2.76 gears-definitely a weak link for anything other than casual highway cruising. To fix that little problem, we received from National Drivetrain a 3.91 ring-and-pinion set. So much for the torque-multiplication dilemma. To transfer that torque equally to both axle shafts, we selected a Powertrax Lock-Right unit.

The Lock-Right replaces your existing spider gears with an automatic locking gear set. This is a great upgrade for do-it-yourselfers who want to keep their street car...well...streetable, but are looking for a little straightline advantage.

It works something like this: During typical driving conditions, a Lock-Right-enhanced differential allows your axles to turn at different speeds (or differentiate), much like an open or limited-slip differential gear set. It's a bit clicky-sounding during sharp, low-speed cornering (when the meshed teeth overrun each other), but this is perfectly natural. Since the unit is spring-loaded, under straightline operation (both axles turning in unison) the axles are continually locked together. That's the key to full power transfer to the rear wheels and a solid hole shot.