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.
Step One for any rearend work...
Step One for any rearend work is to drain the gear lube.
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.
We pulled the brakes so we...
We pulled the brakes so we could clean, sandblast, and paint all the parts and replace the shoes.
With the rearend pointing...
With the rearend pointing straight up, loosen the nuts that secure the center section to the housing and remove them. We secured our housing to the lift so it wouldn't move while lifting the center section out.
Now you can lift out the differential....
Now you can lift out the differential. Unlike the 8 1/4 rear, with the 8 3/4 you must remove the ring gear in order to remove the thrust block shaft. If you are changing gears, knock the pinion gear out with a rubber mallet.
Here are the five nuts (arrows)...
Here are the five nuts (arrows) you need to remove in order to pull the axles. A hole in the axle flange provides access to loosen the nuts with a socket. With the nuts removed, simply pull the axles out of the housing.
Take a small punch and index...
Take a small punch and index one bearing cap to the housing so you can return the caps to their original position during installation. NOTE: If you are changing the gears, remove the pinion nut with an impact wrench before you remove the differential from the casing. The nut is torqued to 240 lb-ft, so without the differential in place you cannot hold the pinion gear in order to loosen the pinion nut.
When you remove the ring gear,...
When you remove the ring gear, remember that the bolts are left-hand thread.
In order to remove the spider...
In order to remove the spider gears you must first remove the roll pin (arrow) that holds the thrust block shaft in place. Do this by tapping it out with a small drift pin.
With the roll pin removed,...
With the roll pin removed, you can now tap the thrust block shaft out of the spider gears.
With the center section empty,...
With the center section empty, score the bearing race with a cut-off wheel. Next, break it off with a chisel blow to relieve the tension, and tap the race off. NOTE: Be careful not to cut into the center section with the cut-off wheel when scoring the race.