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1970 Chevy Chevelle 9 Inch Rearend & Limited Slip - Mail-Order 9Out Of The Box And Built Your Way From the February, 2009 issue of Chevy High Performance By Sean Haggai Photography by Sean Haggai
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Quick Notes
What We Did
Assembled a complete crate rearend from Currie Enterprises
Bottom Line
It's as easy as ordering your favorite pizza It's kind of like ordering a pizza just the way you like it and with all your favorite toppings, only instead of ordering extra cheese and pepperoni, you're getting your choice of a limited slip and disc brakes. It gets even better: You can get as custom as you want or just a simple rebuild with a stock housing. This is where Currie Enterprises out of Anaheim, California, comes into play, as it can provide you with the most out-of-the-ordinary, one-off custom rearend the mind can dream up. If you feel like you have to have it, Currie can certainly build it to spec, assemble it, and have it shipped right to your door. In our case, the '70 Chevelle we've been toying with is transforming from an all-drag A-body with a spool to a dual-purpose warrior that's more street-friendly with a 9-inch rearend and a limited slip. We needed something in the Chevelle to make its new home on the street more user-friendly and something to stand up to its big-block power. A rearend's job is to house the gears and the axles and to make certain the power is delivered to the ground to get your sled moving. Without the right gearing, axles, or housing, an engine can make mincemeat out of those parts in one fell swoop. Gears can explode under extreme load conditions and axles' splines can shred instantly-all the more reason for a beefy rearend. Why a 9-inch, though? Not only does this rearend have a massive following, but its aftermarket parts are readily available-far more than any other rearend on the market. And let us not neglect to mention that the 9-inch carries an additional strength factor that no other rearend carries: a third pinion bearing on the head of the pinion gear, as opposed to just the normal two on the pinion shaft that other rearends have. If you aren't applying all that energy to the ground and to the tire, it's wasted effort; high horsepower numbers are cool on paper, but unless those numbers are backed up with track times, no one cares much. This is why it's important to get your rearend set up correctly and to have it be able to handle the chores you have in mind for it. For us, we went with the stock housing and axle lengths, a 3.50:1 gear ratio, limited slip, 31-spline axles, and a 1350 yoke. We also decided drums wouldn't sit right on this Chevelle so we opted for Currie's 11-inch Explorer disc brake package. And because this Chevelle will be seeing double duty as a street-ripper and weekend drag car, we had Currie drill out dual bolt patterns in order to fit a broader range of wheels for both the street and strip. Follow along and see what goes into a build, and while we won't be installing this rearend into the Chevelle just yet, we'll follow up with a complete step-by-step piece shortly.  Currie builds all of its rearend...  Currie builds all of its rearend housings in-house by hand. Each bare rearend housing is set on a specific jig, and in our case this rearend was set up for a '70 Chevelle A-body. The axlehousing tubes are welded on and the studs for the differential cover are installed as well.  It's important that the housings...  It's important that the housings remain true and straight. Every housing is thus sent to a press for accuracy, where it will also be straightened when necessary. At this phase, pressure is applied to knock out all the kinks and make sure the axles have a solid base.  Currie's axles begin their...  Currie's axles begin their lives as stocked pieces in the shop. Currie carries around 36 different core forgings for different splines and offset applications. From there, once the company receives your order, it tailors each axle for length, bolt patterns, and splines.  For our '70 Chevelle, we decided...  For our '70 Chevelle, we decided to go with a 31-spline axle configuration because of its popularity and cost-cutting advantages. The 9-inch does not need C-clip notches cut into the axles because the axles are positively retained in the housing.  Up next, the third member:...  Up next, the third member: Our 3.50:1 gears were assembled with a limited slip, and once they were torqued down, they were miked for accuracy.  Backlash is crucial when setting...  Backlash is crucial when setting up the gears, and Currie will do this for you whether you have the company build the rearend or not. Our backlash came in at 0.0010 inch;...  ...this wear example illustrates...  ...this wear example illustrates the perfect pattern the gears should create with the proper lash. Any incorrect parameters can cause problems with the gears. Too tight will generally burn your gears up, and too loose will generally create slop and an annoying howling sound.  With the hard stuff out of...  With the hard stuff out of the way, it was time to assemble our 9-inch rearend. Here, Gonsalo Sepulveda double-checks the rearend housing measurement prior to piecing together the components. The driver-side housing tube came to 18.917 inches while the passenger-side tube measured 18.789 inches.  To prepare for the completed...  To prepare for the completed third member with limited slip, Sepulveda applied Permatex Silicone before and after he laid down the gasket for a perfect seal, which will prevent any leaks in the future.  The completed 3.50:1 third...  The completed 3.50:1 third member is then cradled into place. We tightened the supplied 3/8-inch-24 nyloc nuts down in a crisscross pattern starting with the top center, bottom center, right side, and then the left side. Sepulveda then torqued the entire assembly to 40 ft-lb.  Next, the four T-bolts were...  Next, the four T-bolts were installed for the disc brake backing plate.  Currie's disc brake backing...  Currie's disc brake backing plate features an integrated parking brake system as well. After the T-bolts were lined up with the gold retaining ring, the backing plate was tightened down by torquing it to 40 ft-lb.  We had these axles drilled...  We had these axles drilled and threaded to accept two different lug patterns. Sepulveda installed the studs into each axle and impacted them on.  Sepulveda then installed the...  Sepulveda then installed the axle bearing/seal assembly, Explorer brake spacer ring, and gold retainer ring onto each axle. From there he pressed the whole assembly together.  After the axles were guided...  After the axles were guided into their new homes, a liberal amount of lube was applied onto the axle splines to help them slide into place. Once the splines were lined up, all it took was a quick push to seat them properly.  With the axles firmly in place,...  With the axles firmly in place, it was time to install Currie's 11-inch Explorer disc brakes and calipers.  The last step was to install...  The last step was to install the rubber brake lines to each backing plate. While we went with the rubber units, Currie offers braided ones as well.  There you have it. Our Currie...  There you have it. Our Currie crate rearend is ready to swap into our '70 A-body Chevelle. Stay tuned-we can't wait to get this unit into the car and make some runs with it!
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