The basis for the 9-inch rearend in Project Street Fighter is a Fab 9 housing from Chris A
Those who have experience building or racing cars know that the weakest link of your drivetrain can cost you dearly. Many hobbyists start out with modest intentions and under-build their cars, only to find that what they really want is something indestructible and worry-free. For the kind of abuse these cars get, it's no wonder that some guys are constantly chasing down problems and making temporary bandage fixes. This is not something we intend on doing with project Street Fighter. Our '66 Mustang coupe is being built to race and to flog out on the street. Every part we're using needs to be able to withstand the tortures of power and traction.
Our original six-cylinder Mustang rearend was not going to last one night with the 427ci stroker Smeding powerplant we've got in store for it; we had to go bigger and better for all parts that are going to see this dynamo's prodigious torque. With plans to use Chris Alston's Chassisworks' G-Bar rear suspension system (eliminating the leaf spring setup), we would be using Chassisworks' 9-inch housing as well. It came with all the necessary bracketry to attach their new four-link suspension, making the conversion complete. We got the housing powdercoated satin black at AR Powdercoating in Anaheim, California, which you can read more about in my column (see "The Last Word," page 98). Powdercoating is durable, good looking, and fairly inexpensive, making it a favorite option.
The bombproof guts of a Ford 9-inch are what really make it one of the strongest rear ends out there. A GM 12-bolt may be lighter and take less power to operate, but when it comes to setup tolerances, it's hard to beat a 9-inch. Among the biggest checks in the "plus" column is the option of having one or more alternate carrier assemblies (or third members) with different gear ratios or differentials. These can be easily swapped track-side or in your garage in just an hour or two. When it comes to building and setting up a 9-inch rear, few outfits have more experience than the pros at Currie Enterprises, and that's where we went to help us get this rear end together.
The type of driving you intend to do with your project car determines the type of carrier and what gear ratio you want. For our application, we chose a Detroit TrueTrac posi. This posi doesn't use clutches like most, but rather a set of gears that seamlessly apply the power to both wheels under load. A smooth operation was very important to us, since we will be driving the car on the autocross and the road course. The Mustang will constantly undergo load changes--so the traction needs to be predictable, and the TrueTrac provides that in spades. We chose a 3.25:1 gear ratio to give us a little more speed in each gear. If your power is in the higher-rpm range, you may want to choose a numerically higher gear, such as 3.50:1 or 3.70:1, to get you into that power sooner. Currie uses gears by Midwest Motive in all their assemblies, and they have proven strong enough for the drag racers, rock crawlers, and road racers they service. To go along with the built-tough theme, we chose a 1330 yoke over its original 1310 model.
The last decision to make is what to use for rear brakes. Many cars can get away with drum brakes in the rear; for street driving and drag racing, there isn't much need for a ton of rear brake. In fact, that's the option editor Hunkins selected for his '68 Chevelle, which sees more dragstrip use than road course abuse. Our Mustang, however, will need some major braking back there. We chose a matching set of Wilwood's 13-inch rotors to go with our fronts, and four-piston Superlight calipers. These brakes are fitted with an internal parking brake drum, so you can still park on hills without worry.
With all the parts chosen, we needed to get it all together. The guys at Currie walked us through, step by step, on how to put together a rear end that is built to last. Currie's assembly experts, Rueben and Gonsalo, have built rear ends for over 15 years collectively, and they make it look so easy. Here's what you can expect to do when you assemble your indestructible 9-inch rear.
|WHERE THE MONEY WENT |
|Wilwood rear brake kit ||$1,701.95 |
|Chassisworks Fab 9 housing ||$1,139 |
|Currie 31-spline axle package ||$459.95 |
|Currie installation kit and hardware ||$124.95 |
|Powdercoat housing ||$20.74 |
|Midwest Motive 3.25:1 gearset ||$199.95 |
|Eaton TrueTrac posi ||$609.95 |
|Currie Sportsman 9-inch case ||$239.95 |
|Currie 1330 yoke ||$106.60 |
|3 quarts (non-synthetic) gear oil ||$27.98 |
|Total ||$4,631.02 |
Once you've selected a 9-inch housing, the first step is to measure for axles. For a refer
The Fab 9 housing from Chassisworks doesn't come with the third- member bolts installed, s
Currie will build your axles to the length you need, but you'll have the option of either
Here we are at another hydraulic press--get the feeling that one of these is kind of impor
The Currie pinion support comes with the bearing races already installed. We pressed the i
Here, Rueben, the assemblyman at Currie, adjusts the side load on the bearings. He does th
To check backlash, you install the caps over the bearing adjusters, and get them tight. Wh
Since the backlash was within spec (way to go, Rueben!), he torqued the caps down and inst
Before dropping the third member onto the housing, apply a steady 1/8-inch bead of silicon
The final check for proper clearances and alignment is to paint the gears with a special l
The third member may need some persuasion over the studs, so use a soft-faced mallet to fo
Our next step was to install the brakes. There are four anchor bolts on each bearing housi
When the axle bearings get pressed on, remember to keep the axle retainer trapped between
Here is the tricky part: You will need to get the axle retainer nuts started, and you won'
The last step is to slip the brake rotor over the axle, then the caliper onto the rotor. T