Mopar Rearend Replacement - Project B3 Gets Rear Ended

Whether your Mopar is a street car or a dedicated race car, chances are it's overpowered. Tire shredding, axle snapping, u-joint exploding torque is something even stock Mopar engines are known for. While too much power is not necessarily a bad problem to have, the driveline behind the engine must be built to withstand the power, or reliability will suffer. Since reliability is one of the keys to our bracket racer project, we had to decide what rearend would best suit our needs. While an 831/44 differential would probably suffice if built properly, it still wouldn't be as tough, or last as long as a 60-style rearend.

Since we showed you how to narrow and assemble your own Dana previously, in this issue we'll give you another option. Strange Engineering is fabricating an all-new 931/44 rearend housing called the Strange 60, and when stuffed with their tough internals, the Strange 60 is virtually indestructible.

If you've been following project B3, you know that our engine is a 451ci, low-deck big-block that makes well over 600 hp. While a properly built 831/44 rearend would handle this kind of power for a while, we're looking for years of reliability from this bracket racer, so we decided to spend a few more dollars and upgrade to one of Strange Engineering's Strange 60 differentials. The Strange 60 is based on the same Dana 60 rearend that Chrysler installed in their most brutal Hemi and 440 Six-Barrel-equipped street cars, and features the same, massive, 931/44-inch ring gear. The Strange 60 can be custom ordered for any application from a stock street car to the wildest race car. our car is a dedicated racer, so we had the guys at Strange set up the rearend to take some serious abuse. If your car is a street car, you can save a few bucks by ordering your rearend with more economical components.

There are several reasons a drag car needs heavy-duty components in the rearend. First, race engines simply make more power and torque than the average street engine. Second, race stall converters are usually far looser than street converters; our Dynamic 8-inch converter will flash in the neighborhood of 5,000 rpm, again applying more torque to the rearend. The third, and most important factor, is the soft compound slicks that adorn the rear wheels of most race cars. Slicks, unlike street tires, won't spin when the car is launched, and, therefore, incredible forces are transferred to the car's driveline. Street tires will spin when overpowered, relieving the stress on the rearend, axles, and driveshaft, but slicks grab and hold, exposing any weakness by breaking driveline parts. Since we'd rather be at the track racing than in the shop repairing the rearend, we asked the guys at Strange to use some of their best components when building our Strange 60.

A nice feature of all Strange 60 housings is, unlike factory Dana 60s, the axle tubes are fully welded to the center section of the rearend. This prevents the tubes from twisting in the housing under high loads. Since it is imperative a drag race car's rear wheels turn at the same speed throughout the run, we decided to run a spool in our rearend. A spool, unlike a Sure grip, is simply a solid connection between the ring gear and both axles, forcing the rear wheels to spin at the same speed. We don't recommend a spool for street applications for obvious reasons. Around corners, especially in the rain, the inner wheel will spin at the same rpm as the outer, but since it has less distance to travel, it will slip. This causes traction issues that could lead to loss of vehicle control, so if you're building a rearend for a street car, we recommend a Sure grip differential. Since our Barracuda will be raced for years to come, we chose Strange's lightweight Pro Spool for our application. This is a tough piece, and when matched with a pair of 40-spline race axles it should give us years of reliable service. Our 40-spline axles are solid, and we had them fitted with 51/48-inch wheel studs for extra durability. Since we'll be running this car in the quarter-mile, we opted for 4.30-ratio Pro-gears, which should match our tire size and power combination well, pulling us through the traps at some 7,000 rpm.

our Barracuda will retain its factory suspension component locations, so we had our new rearend built to factory A-Body dimensions. If your car is back-halved, mini-tubbed, or otherwise narrower than stock, Strange can custom build your rearend to fit your application.

To complete our rear suspension, we'll be installing Mopar Performance Super Stock leaf springs, an adjustable pinion snubber, and Strange double adjustable rear shocks. This is not an exotic setup, but a reliable suspension package that should get our project car hooking up well enough for some sub-1.50-second sixty-foot times. But enough about theory, let's install our new rearend.

With the back half of our suspension installed in our project car, we're a little closer to making it to the track. Be sure to follow future issues as we'll continue our project by installing the engine and transmission, front suspension and brakes, wire and plumb the car, lighten it up with fiberglass body parts and polycarbonate windows, then finally finish up the interior. We're still a long way from the track, but each step is getting us closer. The car is just about to achieve "rolling chassis" status and that should help motivate us to quickly complete our bracket racer.