FAB9 9 Inch Rearend - Baby's Got Back
Project True 10.5 Gets A Bulletproof FAB9 Rearend
From the August, 2010 issue of Chevy High Performance
By Henry De Los Santos
Photography by Henry De Los Santos
Whatever your high-performance rearend needs, we're pretty fortunate today to have such a wide selection. And while there are plenty of stout 10- and 12-bolt setups getting quick cars down the quarter-mile, there may come a time when you'll need to step up to a 9-inch assembly. That time has come for our True 10.5 Camaro; it's a perfect candidate for this type of upgrade.
You can forget about all the Blue Oval connotations from the Bow Tie purists, because these days, the famed 9-inch setups are manufactured with all-new components and are far superior over the factory castings. We're talking first-rate materials with a custom-built FAB9 housing from Chris Alston's Chassisworks. And to complement the fabricated housing, we're planning to add robust internals with a full-floater assembly, gun-drilled 40-spline axles, centersection, and brakes from Strange Engineering.
Accurate measurement of the...
Accurate measurement of the tire and wheel is extremely important when filling out the Chassisworks' rearend worksheet. The worksheet will determine your correct housing dimensions. With the backside of the wheel facing up, a straight-edge is placed against the fully inflated tire sidewall. Measuring through the center hole to the ground reveals the true tire section width (dimension D on worksheet), and measuring to the wheel mounting surface gives us the installed wheel backspacing (dimension C).
Prior to ordering, you'll...
Prior to ordering, you'll have to measure the width of car from the inside quarter-panel lip to opposite quarter-panel lip for the total length. The measurements we listed on our worksheet were perfectly matched and you can see how well the rearend fits our chassis.
Another important measurement...
Another important measurement is sizing up the outside width of the framerails. Again, this is just one of many critical dimensions needed in order to size up your custom rearend perfectly.
Chassisworks' axle brackets...
Chassisworks' axle brackets feature a scalloped design to remove unnecessary weight beyond the mounting holes. To improve the axle bracket's ability to resist hole elongation from repeated use without adding excess weight to the rearend housing, doubler plates are utilized.
The one thing you need to understand when ordering up a FAB9 housing is that precise measurements are your number-one priority. You're going to see us reiterate that a lot, but even so, we can't say it enough. Fortunately for us, our chassis guru Bill Hickok of Hickok Race Cars is well versed with Chassisworks' detail-oriented worksheet. His experience allowed us to take all the correct measurements and fill out the worksheet rather quickly. It's worth mentioning that once you've entered your dimensions, you do have to sign for it, acknowledging that you're taking full responsibility for the information supplied. That's right, once they build it to your specs, you're completely responsible for it.
But what happens after you fax in your paperwork? Let's just say quite a bit of machining, welding, and even more measuring. Don't take our word for it; follow along as we show you the incredible amount of work that goes into building a FAB9 rearend-it's sure to open your eyes and give you a whole new level of appreciation, especially for something we can simply order over the phone for our dragstrip terrors.
What Is It
The toughest 9-inch rearend we've ever seen
The Final Word
Measurements are vital, so check twice and get it right
Avenger 4-Link FAB9 start at $1,789; other FAB9s as low as $459
Prior to TIG welding, the...
Prior to TIG welding, the bracket components are bolted tightly together to ensure the parts remain in the correct position. The doubler plates are first tacked, then completely welded to the outside of each bracket. Multiple gusset tubes are then welded in place to stabilize the bracket assembly.
To ensure that the housing...
To ensure that the housing fits the car exactly, Chassisworks has developed an extremely detailed custom rearend worksheet that must be completed. Worksheet instructions are included, explaining specific measurements and any necessary calculations. During housing assembly, the worksheet will be referred to for the required dimensions. As daunting as it may seem, it's this attention to detail that will see your rearend fit perfectly for your application.
The pinion centerline gauge...
The pinion centerline gauge bolts directly to the housing studs and provides an easy reference point for measuring the axletubes. With the housing positioned square to the bandsaw, tubes are cut to the lengths calculated from the custom rearend worksheet and instructions.
Next, the TIG-welded axle...
Next, the TIG-welded axle bracket assemblies are slid over the axletubes, and the centersection and brackets are bolted securely to the in-house rearend assembly fixture. Large bars extend through the fixture and housing, allowing the brackets to be squarely positioned at the width the worksheet specifies.
This split images shows a...
This split images shows a trimmed-down version of the Chassisworks rearend assembly fixture that's available and can provide the same level of accuracy for any shop. As shown here, the fixture is simply secured in a vise, but it can also be bolted to a workbench for more regular use.
Again, bolts are used to keep...
Again, bolts are used to keep the parts in their correct position and minimize any heat distortion during welding. Both sides of the bracket are accessible in the fixture, allowing the brackets to be welded the full 360 degrees around the tube without unbolting the housing from the fixture.
Everything is right out of...
Everything is right out of the catalog, and Chassisworks has a selection of folded, tapered back braces designed to significantly strengthen the centersection and axletubes. This particular installation required the brace to be cut into three pieces with some minor trimming for proper clearances.
Once the back brace has been...
Once the back brace has been fit and tacked into place, welding is done in short segments, alternating from top to bottom and right to left. This gives the material more time to dissipate heat, minimizing heat distortion.
The Strange Engineering floater...
The Strange Engineering floater spindles, as shipped (left), must be turned down on a lathe to achieve a correct fit for each axletube. Custom fitting is required to account for manufacturing wall-thickness tolerances in the axletube material. This image shows the floater spindle before and after being machined.
The spindle snout base is...
The spindle snout base is locked into the lathe chuck and material is removed from the outer surface to precisely fit the axletube. Dimension M from the worksheet is measured from the axle flange toward the axletube and is left unmachined to create a shoulder stop for the spindle ends at the correct housing width.
The housing-fixture bar is...
The housing-fixture bar is fitted with a centering end specific to the floater spindles; this holds them perfectly square and aligned with the ring gear. A digital protractor is then used to correctly clock the spindle before filling the four holes with rosette welds.
After the floater spindles...
After the floater spindles have been completely welded to the axletubes and the housing has had time to completely cool, the fixture bar is loosened and the centering end is removed. Because the floater ends are perfectly aligned, the centering end slides in and out of the spindle smoothly without force.
Once all the welding is complete,...
Once all the welding is complete, the housing is removed from the assembly fixture and carefully pressure-tested to ensure there are absolutely no leaks. With a successful quality check, the housing is foam-packaged and ready to be shipped. With our FAB9 complete, we just need to assemble the remainder of the components, including our Strange Engineering centersection and gun-drilled, 40-spline axles. We'll show you that in the coming months as a complete Step-By-Step piece.