Making huge horsepower for drag racing puts incredible strain on drivetrain components, especially the rear-end assembly. Mark Williams Enterprises, a company known for heavy-duty driveline parts since introducing warranted forged axles back in the ’70s, now offers a package bundling their most advanced components into what they term the Ultimate 9 Ford rearend assembly.

This setup builds upon Mark Williams’ pioneering modular aluminum 9-inch housing design from 1990. The current housing utilizes a strong aerospace aluminum alloy, which Mark Williams claims offers 30% more strength than typical 6061 aluminum. Mark Williams performs all the intricate CNC machining on these housings in their Louisville, Colorado facility, ensuring high precision for component fitment.

The key parts defining the “Ultimate” package reside inside this robust housing. It includes Mark Williams’ Ultimate Hi-Torque axles which employ super-strong 300M steel construction.

Mark Williams backs these specific axles with a confidence-inspiring 10-year warranty against breakage. Racers can order them in either flanged or full-floater styles to suit their specific chassis and safety requirements. To reliably handle very high drive shaft speeds, the top-tier pinion support option available for this assembly features dual angular contact bearings that incorporate ceramic balls, providing superior RPM capability compared to standard bearings. Finishing the internal package are special 10-inch pitch diameter rings and pinion gears. Mark Williams developed these gears specifically for ultra-high horsepower applications in collaboration with gear manufacturer Gleason Corp.

Mark Williams makes these critical gears from tough 9310 alloy steel and then subjects them to an extensive list of processes. These processes include: precision grinding for accuracy, shot-peening for fatigue strength, friction-reducing REM micro-polishing, and a sub-zero cryogenic treatment for maximum durability under extreme shock loads found in drag racing.

Like their other modular units, Mark Williams builds these Ultimate rearends as soon as the customer finalizes their order. Customers select the housing width and choose mounting brackets designed for common 4-link or solid suspension setups. For builders seeking maximum housing stiffness, Mark Williams also provides an option for strong steel axle tubes instead of standard aluminum tubes.