Marc Christ
Brand Manager, Modified Mustangs & Fords
June 4, 2012

We took a month off from our latest four-eyed Fox project car last month. But if you've been following along, we've completely gutted it, smoothed the engine bay, welded in our subframe connectors, and mocked up the engine, trans, and rollbar. Now the car is at the body shop and we're looking for things to do while it's gone.

In the last installment, we jazzed up our FRPP crate Coyote with a Turn Key Engine Solutions belt drive, a Boss intake and throttle body, BBK long-tube Coyote swap headers, a Moroso oil pan, and an FRPP alternator kit.

Since we cleaned the underside of the car, we've discovered that the pinion seal is leaking pretty badly. We could just go through the 8.8-inch rearend that's there, but we found this a good opportunity for an upgrade. Besides, we wanted to narrow the rear by 2 inches on each side anyway, and there's no time like the present.

So we called on Chris Alston's Chassisworks for one of its Fab9 rear housings. The company offers a wide selection of 9-inch housings for stock-style suspension or custom-fit applications. We're locked into our Kenny Brown Performance stock-style suspension kit, so we decided to go with the OEM-replacement housing. The housings start at $769 for a mild-steel housing with none of the goodies.

The goodies range from 4130 steel construction, wheelie-bar brackets, spherical control-arm mounts, and back braces. We chose the mild-steel construction, urethane control arm mounts, no integrated antiroll-bar mounts, and 2 inches narrower than stock on each side.

One great benefit of working with Chris Alston is the company's ability to work with details like the brand and type of brakes and internals that you'll be using. It even works closely with Wilwood and Strange, and can sell you everything you need from each of those companies. We'll get our stuff directly from the manufacturer, but when we received our housing, also included was a quote for everything we needed from Strange and Wilwood, complete with part numbers and pricing.

The Guts

We chose Strange Engineering to source the internals of our rearend--partly because Chris Alston's Chassisworks made it so easy, and partly because we knew it had some great new products to offer in the street/track sector.

The centerpiece of the moving parts of our new 9-inch rearend is the Strange Pro HD aluminum center section (PN PRF180; $2,030.50). It consists of Strange's new Pro HD aluminum housing with through-bolts, 4.57 Motive gears, a billet-aluminum yoke and pinion support, and Strange's new S-trac differential, and comes as a complete drop-in unit.

The new Pro HD aluminum housing (PN N2303; $489.50) is the next-best aluminum 9-inch case from Strange after the Ultra Case. It's designed for drag racing applications, as well as abusive high-performance street/strip applications. Made from 206-T4 heat-treated aluminum, it's stronger than most common aluminum cases. The shape of the case promotes oil scavenging for demanding street and high-endurance applications--like ours. The billet aluminum pinion support even has a unique oil channel machined into it to maximize oil flow to the pinion bearings.

The S-trac differential (PN N1982; $995), also new from Strange, is a helical gear differential that offers smooth and progressive power transfer. If one of your rear tires begins to slip relative to the other, a separating force is created between the pinion gears and side gears. This separating force generates an internal frictional force, which slows the spinning wheel and sends power to the wheel with most traction. It, too, is designed for the most abusive street/track applications and designed for use with 35-spline axles.

The billet aluminum pinion support (PN N2322; $149.50) comes with 7?16-inch ARP bolts, O-ring, and cups installed. The gear set we chose has a ratio of 4.57 (PN RS07890456; $169), is made of 8620 steel, and should provide us plenty of torque multiplication for launches and acceleration when coming out of turns on the open track. Though it's pretty steep, our double-overdrive should give us a bearable cruise rpm in Sixth gear--though we can't calculate it until we've decided on a tire size.

For axles, Strange sent us its 35-spline S-series alloy axle package (PN P3502; $379.20), which comes with alloy axles, bearings, and a choice of 2- or 3-inch studs. These might be a little overboard for our application, as we're going to be making somewhere in the 430-rwhp range, but this leaves us plenty of room to grow under the hood later on.

Next month, we'll bring you the first installment on the paint and body. Summit Racing has supplied everything for this part of our project, and we should be ready for reassembly soon.

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