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How to Build an Indestructible 9-inch Rearend - Bombproof

In the quest to run 7s in a Fourth-Gen Camaro, we build an indestructible 9-inch rearend

Stephen Kim Jan 22, 2015
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My oh my how times have changed. Back in the good old days of stinkbug stances and $2.99 Big Mac meals, a stock 12-bolt rearend could handle just about all the power you could throw at it. These days, an LS3 small-block with nothing more than long-tubes and a mild cam kicks out enough power to give a factory 12-bolt a run for its money. With great power and grip comes tremendous driveline stress, and the astounding hook provided by today’s suspension and tire technology only compounds the situation. So when plans call for dropping in a supercharged 1,500-horsepower LS7 small-block in an ’00 Camaro drag radial race car, you better build yourself a bombproof rearend. Thanks to Chris Alston’s Chassisworks and Strange Engineering, a duo relied upon by countless hard-core drag racers, that’s exactly what we did.

Destined to compete in today’s ultra competitive drag radial classes, our ’00 Camaro project car will need to run low-7s in the quarter-mile to hang with the big boys. Work has already started on an RHS-based engine combo that will push our fourth-gen well past 170 mph through the traps. Although the aftermarket offers several different turnkey rearend packages for fourth-gen F-bodies capable of holding up behind an 8-second combo, pushing 1,500-plus horsepower through a 3,300-pound chassis requires getting a bit more creative. That’s why we decided to combine a Chassisworks chromemoly FAB9 housing with bulletproof Strange axles and an aluminum centersection. The end result is a rearend assembly that’s durable enough to survive behind an Outlaw 10.5 car yet retains the stock suspension mounting points in order to remain legal to the rulebook.

In the coming months, we’ll be covering the buildup of our drag radial race car in greater detail. In the meantime, if you need to build a rearend that can handle all the power you can throw at it, here’s how to do it.

Bombproof 9-inch
Description Part No Price
Chassisworks FAB9 housing, base price 84F40-F11 $1,643
Strange Ultra aluminum centersection PRF225 $1,728
Strange 40-spline axles P1014 $633
Strange Pro Race rear brakes B1706WC $589
Grand Total $4,593

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01. The bolt-in Chassisworks FAB9 housing has all the bells and whistles a drag racer could dream of. The center housing and back brace are built from flat sections of rugged 4130 chromemoly steel sheetmetal that integrate into the 3-inch diameter axletubes. Internal tube gussets further fortify the housing, and seams are robotically spray-arc welded for consistency. The folded back brace spans from the outer edge of the back panel to the axle mounts and are tapered to reduce weight. In fact, the housing is both stronger and lighter than an OEM unit.

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02. The FAB9’s antiroll bar mounts double as a mounting point for a coilover conversion setup. The antiroll bar slips through the mounting tube and rides on bearings positioned at each end. This completely eliminates the potential for binding regardless of the pre-load placed on the endlinks. The coilover brackets allow changing ride height without compromising the spring or shock travel.

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03. The rules on what does and doesn’t qualify as a stock suspension varies by sanctioning body, so the FAB9 housing retains the factory fourth-gen Camaro control arm mount, Panhard bar mounts, and spring perches. The control arm mounts have several boltholes to enable fine-tuning the instant center.

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04. The stock fourth-gen Camaro torque arm attaches directly to the differential assembly. In contrast, the FAB9 housing incorporates three heavy-duty torque arm mounts located at the 1 o’ clock, 3 o’ clock, and 5 o’ clock positions around the centersection of the housing. The FAB9 housing is compatible with Chassisworks’ own torque arm, and alternately the company offers an optional adapter that allows most aftermarket torque arms to bolt right up.

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05. Multiplying engine torque by the First gear ratio and the ring-and-pinion ratio gives a rough approximation of how much torque the axles must endure. In the case of our Camaro, that figure comes out to over 6,000 lb-ft. Consequently, Strange set us up with a set of its 40-spline Pro Race axles that can handle over 10,000 lb-ft. They have been gun-drilled to reduce mass.

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06. At the low-7-second level, running on 1/2-inch wheelstuds is a risky proposition. As such, Strange supplied a set of its 5/8-inch chromemoly studs. They secure to the back of the axle flange with locknuts. To reduce rotating weight, Strange cut lightening windows into the axles flanges.

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07. Behold one of the baddest centersections known to mankind. The aluminum Strange Ultra Case features a 3.812-inch bore, a super-sized pinion support, and main cap studs that extend all the way to the front of the case for extra support. Strange offers the centersection in fully assembled trim—complete with a spool, a large-stem ring-and-pinion set, and a chromemoly 1350 yoke—for about $1,728.

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08. Not too long ago, fitting a 40-spline spool inside a 9-inch rearend required a 2-inch diameter spool bearing journal. That’s fine for many applications, but marginal in heavy door-slammers producing thousands of horsepower. To address to problem, Strange increased the case diameter from 3.250 to 3.812 inches, which frees up space for a 2.250-inch spool bearing journal diameter when using a 40-spline spool. This substantially increases strength and provides a far more solid foundation for the ring gear. Speaking of ring gears, we ordered up a 3.50:1 Motive Pro Drag gearset.

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09. The pinion support area in a stock 9-inch is notoriously weak, but Strange has thoroughly addressed that problem with its Ultra Case. The mammoth pinion support houses a 35-spline pinion, which is quite a bit larger than a stock 28-spline pinion. As such, the pinion support is extra long and accommodates an oversized bearing. It’s anchored by 12 high-strength bolts.

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10. The Strange aluminum caliper brackets also serve as the axle retainer plates. Since it’s a closed design that covers the entire 360 degrees around the axle, it must be dropped into position before pressing on the axle bearings. After first pressing on the axle bearings in a press, the “wedding ring” must be pressed in to retain the bearing onto the axleshaft.

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11. Ordering up a turnkey centersection eliminates most of the monkey business involved with setting up a rearend. After laying down the gasket, the centersection is positioned onto the rearend housing and secured with 3/8-inch bolts tightened to 35 ft-lb.

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12. Using the supplied 3/8-inch bolts, we torqued the caliper bracket down to 35 ft-lb. This FAB9 housing came equipped with the popular big, late-style Ford 9-inch housing ends. In the future, removing the axles will be as simple as unbolting the caliper bracket, then sliding the axles out. There are no C-clips to fiddle around with.

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13. Strange finished off the rearend with a set of its Pro Race steel brakes. The setup utilizes 11.25-inch forged steel rotors that have been slotted to reduce warpage and weight.

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14. The four-piston Strange calipers require minimal setup. After popping in the pads and inserting the through-bolt, they’re ready to bolt onto the caliper bracket. They feature staggered 1.750- and 1.625-inch stainless steel pistons to minimize pad taper, and weigh in at just 2.70 pounds.

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15. The calipers torque down to 35 ft-lb using the supplied 3/8-inch Grade 8 bolts. Achieving proper caliper-to-rotor alignment may require shimming the caliper inward or outward. Since fixed calipers have pistons on both sides of the rotors, both sets of pistons must be bled after the rearend is installed in the car.

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16. The final step in the rearend assembly procedure is adding 2.5 quarts of SAE 85W-140 gear oil into the housing. The Chassisworks FAB9 housing features a slick filler for easy serviceability. There’s a drain plug on the bottom of the housing as well.

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17. By ordering up a fully assembled centersection, the entire rearend can be put together in only 2-3 hours. Stay tuned for more detailed installation information on the Chassisworks antiroll bar and torque arm in the near future.

Sources

Strange Engineering
Morton Grove, IL 60053
847-663-1701
www.strangeengineering.net
Chris Alston's Chassisworks
Sacramento, CA 95828
916-388-0288
www.cachassisworks.com

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