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Bringing Up The Rear—Strange and QA1 give our Nova project stouter underpinnings for the strip

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A combination of parts arrived from Strange to get us started on our path to a more bulletproof rear axle. The S60 rearend design was created in-house at Strange and has additional features and upgrades over the original Dana 60 design.

Written by Derek Putnam

Photography by Michael Fair and courtesy of the manufacturers

A team is only as strong as the weakest link, and the same can be said for a vehicle. Horsepower is plentiful in today’s market, with factory-built cars pushing north of 700 ponies with a warranty in place. But sometimes exercising those ponies will reveal parts that aren’t ready to be team players. Even classic muscle cars, with built engines, transmissions and rearends from the factory, can use upgrades to make them more reliable for street and track enjoyment.

Despite a favorable appeal from many street and race cars that employ it, as well as a host of Strange internal parts, the existing 12-bolt Chevrolet rearend had become a weak link. Combining over 3,800 pounds and over 900 rear-wheel horsepower put a strain on parts and pieces, and we needed an upgrade.

Project Boulevard Boost, our ’70 Chevrolet Nova with a 925 rear-wheel horsepower blown big block powerplant, employed a factory Chevrolet 12-bolt rearend for over a decade. But as we increased its power levels, the once-reliable rearend would start to show some cracks in the foundation.

“The diameter of the ring gear is 8.875-inch on a 12-bolt,” JC Cascio of Strange Engineering said. “They can handle a decent amount of power and abuse, but stepping up to the bigger gear used by a Strange 9-inch Ford design or the S60 will definitely make a difference. Thicker teeth and more contact area help spread the load out more.”

So the decision to step up to one of Strange’s new rearends to handle the abuse was an easy choice. But which one would get the nod: the S60 or 9-inch Ford?

“The 9-inch Ford is the most popular all-around rearend we sell,” Cascio explained. “It’s followed by the S60, supported by a lot of bolt-in complete rearend sales, and finally the 12-bolt. The 9-inch Ford is the preferred choice for a racing application, with the widest selection of gear choices, the option of aluminum or iron cases, plus a lot of available parts, provide a lot of benefit for the 9-inch option.” But don’t count out the S60, Strange’s take on the popular Dana 60 rearend that supported many a Mopar vehicle in the 1960s and 70s. “We’ve always offered a version of Dana 60 rear end,” said Cascio. “About 15 years ago, we started using our own unique castings. The previous housing only would work on leaf spring or aftermarket ladder bar and four-link applications, and when we cast our own design, that allowed us to add versions for GM A-body and G-body platforms, plus the torque arm design for third and fourth-generation F-body.”

After removing the 12-bolt, the first order of business is getting the new S60 housing in the right spot. Rollins centered up a new set of leaf spring perches from Calvert Racing on our existing Split-Mono leaf springs before lifting the Strange housing into place.

As popular as the 9-inch Ford is, the S60 makes a strong argument as a viable choice as well. “The S60 uses a 9.75-inch diameter gear, bigger than the 9-inch Ford does as well as coming standard with 35-spline axles. Prior Dana 60 castings uses shim packs to set backlash and preload on carrier bearings,” Cascio continued. “We went to an adjuster nut to replace the shim packs, allowing the user to use a spanner wrench to cut down on set-up and gear change time.”

The S60 also features 3-inch diameter, .25-inch wall thickness axle tubes, much better than most factory rearends. “A lot of factory rearends had the axle tubes pressed into the center housing and were plug welded,” Cascio admitted. “Strange welds the tubes 360 degrees to prevent twisting and leaking in that area.”

The measurements start with getting the rearend centered on the perches. Once Rollins gets the housing in the right place, the pinion angle is next on the punch list.

The only downsides to the S60 rearend? The lowest numerical gear ratio currently available is a 3.54, and it weighs a little more than the 9-inch Ford as well. “The increase in weight of the S60 versus a Ford 9-inch is somewhat related to the bigger ring gear,” Cascio said. “All told, a similar built S60 is about 25 pounds heavier than the 9-inch.” But of the three rearends Strange offers in both complete assemblies and parts, a similarly optioned S60 will cost less to purchase over the 9-inch or the 12-bolt.

After weighing out the options and prices, we made the decision to go with a S60 rear. Because of a few different parts we would be using in the build, Strange sent us a bare housing and the supporting parts we’d need to assemble it versus a complete ready to bolt in version. Rollins Automotive Speed and Custom got the call to set everything up, and we are quite pleased with the results. Part two of the build will feature an upgrade to disc brakes to complement the new rearend, and we plan to put both these upgrades to the test at the track soon.

Once the measurements are confirmed, Jason Rollins makes a couple tack welds to secure the perches to the axle tubes. The entire assembly is then removed from the car, allowing Rollins to final welding the perches in place.
The rearend is then reinstalled to verify the measurements Rollins set up are still in place after the welding was complete.

Is Assembly Required?

Strange not only offers a wide selection of driveline and suspension components, but complete rear end assemblies based on the Ford 9-inch, Mopar Dana 60 and General Motors 12-bolt designs. But which route should you choose: a complete rearend, or buying the pieces and assembling it yourself?

“For street applications, the bolt-in rearends get the majority of the sales over individual parts,” said JC Cascio of Strange. “A lot of the sales for individual parts come from the racing market, especially 9-inch center sections.”

All the components we used for our S60 rear end are available in a completed rearend assembly from Strange, minus the leaf spring perches from Calvert Racing.

“The previous 12-bolt was set-up with these mounts,” said Jason Rollins of Rollins Automotive Speed and Custom. “They work a bit better with Calvert’s Split-Mono leaf springs, and we wanted to keep that constant in the build. But normally I’d recommend buying a complete rear end from Strange. All the guesswork is eliminated, and the quality is always top notch.”

 

Although it’s easy to rattle can paint a rearend, we sent ours to Powdercoating of Gainesville for a gloss-black finish. They not only handled the housing, but powdercoated the aluminum LPW girdle as well.
With the housing back from powdercoating, parts can start being installed. Rollins starts by connecting our existing Calvert Racing Cal Tracs bars with a new set of U-bolts, followed by attaching the shocks.

Locking in Equal Traction

Sending equal power to both tires is the only way to ensure a consistent launch at the track. But many faced the dreaded clutch-type slip of Positraction units decades ago, as the only option in some cases was to upgrade to a spool, something most don’t recommend for a street car.

“It’s a safety concern,” said Cascio. “When taking a corner, the inner tire wants to turn at a slower pace. With a spool, that can’t happen. It can be easy to spin the rear end out, and from a parts standpoint, it puts a strain on tires, and puts additional pressure on axle flanges and bearings.”

Eaton now offers several choices for differentials, and the toughest one is the Detroit Locker. It offers 100-percent locking action to provide maximum traction to both wheels when needed, while unlocking when different wheel speeds are needed for cornering and tight maneuvers.

 

With the center section ready for installation, the axles are prepared for their rightful spot by pressing the axle bearings in place.
After adding the 5/8-inch studs, the axles are ready to slide into the housing. But before that happens, Rollins bolts the Wilwood brake brackets and parking brake assemblies in place.
With all the mechanical details complete, Rollins bolts the powdercoated LPW rear girdle in place, and then adds a couple bottles of Royal Purple Max Gear 75w-90 synthetic oil to keep everything properly lubricated.
To connect the Turbo 400 transmission to the new S60 rearend, QA1 supplied one of their new carbon fiber driveshafts. We checked the boxes for a 1350-series U-joint and a Sonnex slip yoke, getting the shaft a maximum power rating of 2,000 horsepower. In addition, it weighs 9 pounds less than our old 3-inch diameter steel shaft.

Making the Connection

After getting their start with rod ends, QA1 became a well-known name in the shock and suspension parts. Now, the Minnesota-based company is making waves in the driveshaft market, the first parts group from its advanced materials division.

“The new division is a vision of QA1 founder Jim Jordan,” said Damien Brase of QA1. Jordan first noticed carbon fiber being used in Sprint cars, and decided to embrace the material and bring it to the masses for street and strip applications.

“The driveshaft has to be able to deal with the torque upon launch, but then also for critical speed as you move down the track,” Brase explained.

The carbon fiber material allows QA1 to use a smaller 3.2-inch diameter size versus the larger diameter normally required for a steel or aluminum driveshaft. They accomplish all the winding and assembly in house and the winding of carbon fiber directly relates to strength.

“Every material has a spring rate,” said Brase. “With carbon fiber, the strength is directly related to the angle the fibers are wrapped at. A narrower angle of wrapping the material will affect torque more than critical speed versus a wider angle.” Combined with a weight savings over steel versions, it’s easy to see why more carbon fiber driveshafts are being used.

 

To complete the rear end, a set of Wilwood disc brakes are bolted in place. We will cover the details of that installation in a future issue.

SOURCES

Calvert Racing

661 | 728 | 9600

CalvertRacing.com

 

Eaton

800 | 328 | 3850

Eaton.com

 

LPW Racing Products

717 | 394 | 7432

LPWRacing.com

 

Powdercoating of Gainesville

352 | 377 | 2231

Powdercoatingofgainesville.com

 

QA1

952 | 985 | 5675

QA1.net

 

Rollins Automotive Speed and Custom

352 | 335 | 7223

RollinsSpeedandVustom.com

 

Royal Purple

888 | 382 | 6300

RoyalPurple.com

 

Strange Engineering

800 | 328 | 3850

StrangeEngineering.net

 

Wilwood

805 | 388 | 1188

Wilwood.com

 


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