Bolstering A Godzilla-Powered F-100 Pickup With A Stout Strange Rearend

Our friends over at StreetMuscle have a pretty sweet pickup project coming together. Based on a 1969 Ford F-100, it is set to receive a monstrous Godzilla 7.3-liter V8 built by the experts at Late Model Engines. To ensure it can handle that power and plant it to the pavement, they turned to the driveline specialists to construct an S60 independent rearend, and we checked in to see how it came together.

The 460-cubic-inch Godzilla stroker is documented at 764 horsepower at 7,100 rpm, which means the rearend has a serious job ahead of it. F-Zilla is being built around an Art Morrison chassis with independent rear suspension and a TREMEC six-speed manual, so the driveline has to deliver strength without giving up the advantages of IRS.

That called for something more substantial than simply adapting a traditional Ford rearend. Strange Engineering’s S60 independent rear is a Dana 60-based IRS center section originally developed for the 2010–2015 V8 Camaro, but its construction makes it an ideal foundation for F-Zilla.

S60 Foundation

The Strange S60 independent rear (P/N: H1400-AM; $3,995) uses a 9.75-inch ring gear inside a 206-T4 aluminum housing. Radial ribs stiffen the case, fins add cooling surface area, and the support-style rear cover reinforces the billet main caps. For F-Zilla, the S60 independent rear package (P/N: H1400-AMPKG) provides the center section around which the Art Morrison IRS is built.

“Strange Engineering applies over 60 years of experience and real-world feedback to our entire product line. Strange is a family-owned business that has always taken pride in having direct contact with racers, enthusiasts, and builders,” J.C. Cascio, Director of Business Development at Strange Engineering, said. “We rely on feedback for what we are doing well, and more importantly, where we can improve. Working with customers like Art Morrison Enterprises has helped us design a line of products that are tailored to specific applications, rather than a one-size-fits-all approach.”

While a Camaro rearend might seem like an odd choice for a Ford project, given the vibe of the project and the parameters of the Art Morrison chassis, an independent rear suspension got the nod. Strange’s 9.75-inch S60 gives the truck the IRS architecture it needs without sacrificing the strength required by a 764-horsepower Godzilla.

“The Strange S60 independent rearend assembly is an incredibly strong and reliable unit. Strange Engineering and Art Morrison collaborated to integrate the Strange independent rear into their chassis. The large 9.75-inch diameter ring gear, combined with the 35-spline stub shafts and helical differential, makes for a strong and reliable rear that can handle tremendous amounts of power and torque,” Cascio explained. “The independent rear has many benefits over a traditional solid axle rear. Independent rear suspension provides better ride comfort, improved cornering grip, and reduced unsprung weight. Unlike a solid live axle, an IRS allows each rear wheel to react to bumps and rough road surfaces completely separate from the other.”

Gearing Up

The S60 gets a Dana 60 3.54 gearset (P/N: D3550), giving F-Zilla a 9.750-inch, 46-tooth ring gear and 13-tooth pinion. The matched Spicer gears are machined from 8620 forged steel and heat-treated for durability. The 3.54 ratio is a sensible choice for a high-powered street truck with a six-speed manual. It gives the Godzilla plenty of mechanical leverage without going excessively steep on the final drive.

The ring gear is bolted to the differential before the carrier bearings are pressed into place. The pinion is then installed, followed by the critical setup work that establishes bearing preload, backlash, and the proper ring-and-pinion contact pattern.

“To provide exceptional strength in a lightweight package, this Strange 9.75 rearend is manufactured from SAE Aerotech Material Specification 206-T4 aluminum. U.S. Army and Marine Corps research reports that AMS 206-T4 aluminum housings may be subjected to the most extreme conditions on earth for decades without any sign of deterioration,” Cascio said. “Radial case and support cover design affords an even greater level of rigidity and durability to the Strange 9.75, which, despite the larger gear set, weighs only 20 pounds more than a comparable factory rearend.”

Meanwhile, S60’s 2024-T351 billet aluminum main caps and steel adjuster nuts simplify the setup and enhance the durability. 

“The rugged aluminum cover supports aircraft-grade 2024-T351 billet aluminum main caps, adding yet another level of strength and decreasing deflection. Steel adjuster nuts eliminate the need for shims,” he added. “This makes setup more precise and simple…”

Smooth Operator

For this application, the Strange S-Trac differential (P/N: D3523), a 35-spline, 3-series unit designed for Dana 60 and S60 rearends, got the nod. F-Zilla is also optioned with the helical differential upgrade (P/N: OPRS02-AM).

Instead of clutch packs, this S-Trac uses helical gears to control differential action. Under normal operation, it behaves much like an open differential. When one tire begins to lose traction, the gears create a separating force that generates friction inside the differential and biases torque toward the tire with more traction.

“The Strange 35 Spline S-Trac helical gear differential offers smooth and progressive power transfer, and its superior design and quality make it ideal for the most abusive street/track applications,” Cascio said.

The S-Trac also has a specific lubricant requirement. Strange calls for petroleum-based SAE 85W-140 and warns against synthetic gear oil, friction modifiers, and additives. F-Zilla uses two quarts of 85W-140 gear oil (P/N: OILPKG2Q), matching the specified capacity.

Rock-Solid Connection

At the pinion, Strange adds a chrome-moly 1350 yoke (P/N: U1598) through the chrome-moly yoke upgrade (P/N: OPRS18). The 1350-series yoke accepts a larger universal joint, while the chrome-moly construction adds strength at a critical driveline connection.

“The chrome-moly pinion yokes are important in any vehicle that sees high shock loads,” Cascio elaborated. “This could include hard launches, off-road applications, or any other high-horsepower application. While the cast iron yoke is extremely durable and strong, the chrome-moly yoke provides extra insurance at a reasonable cost.”

For a 764-horsepower truck with a manual transmission like F-Zilla, that extra insurance is inexpensive compared with the consequences of a driveline failure.

Final Assembly

With the ring gear installed on the S-Trac, the differential bearings pressed into place, and the pinion installed, the S60 is set up using its steel adjuster nuts. Backlash and the gear contact pattern are checked before the center section is closed up.

The bearing cartridge is then installed in the housing, followed by the finned rear cover and its reusable O-ring seal. Strange specifies 35 lb-ft for the rear cover bolts and 15 lb-ft for the bearing-cartridge fasteners.

The axle installation brings the independent portion of the equation together. F-Zilla uses GForce Performance Engineering with the axle bolts torqued to 57 lb-ft and secured with blue Loctite. Clearance between the axle hardware and bearing-cartridge bolt heads must also be verified during installation.

“The technicians in the Strange Engineering set-up department have ‘seen it all,’” Cascio said. “Our crew has experience setting up all types of rears up to, and including, Top Fuel rearend assemblies. This is what they do. If a rear doesn’t meet our high standards of quality, it doesn’t leave the building.”

With the Strange S60 set up properly and installed, Project F-Zilla has the hardware to handle its new high-performance mission. For more on the rest of the build, including the Godzilla engine, chassis, and other components turning this 1969 F-100 into a serious street machine, follow the full Project F-Zilla build over at StreetMuscle.