Wouldn’t it be great if you could just take your expensive rear end housing with you when moving to a new race car, or re-utilize it when making changes to your existing car, with only minimal work involved? Now sure, you can cut the housing and re-fabricate it to narrow the axle housings or relocate the four-link brackets, but if there was a simpler, less involved way? Well, unless you’ve been living under a rock, there is a way, and it comes in the form of Mark Williams Enterprises’ Modular line of rear end housings. While we’ll be digging further into what these housings are and how they work in this article, you needn’t look any further than the dictionary definition to get an understanding of what these housings entail.
Mark Williams’ 9-inch housing, derived from the legendary Ford 9-inch.
mod·u·lar [moj-uh-ler] adj.
composed of standardized units or sections for easy construction or flexible arrangement
Just as the definition explains, a modular housing is a relatively recent (at least in the grand scheme of high-end race housings) development, in which the housings are build in modular components, allowing the centers to be paired with any number of bracketry, bell ends, axle lengths, and more, to create an infinitely flexible platform that can be catered and re-catered to any vehicle setup. In this tech feature, we, along with Mark Williams himself and the Colorado-based company will bring you a closer look at modular housings, what they are, how they work, and how they’re changing the face of race housings.
Modular Housing 101
This diagram provides an exploded view of sorts that outlines how the Mark Williams Modular housings fit together. The housing center (top) is paired with the according four-link brackets, spacers, and end bells to create the complete housing.
Mark Williams’ Modular rear end housings were developed to cure the common problem of switching out or modifying standard rear end housings in certain situations that required changes in axle length, four-link bracket placement, mounting points, or other issues, by effectively creating an interchangeable system of components based around a central unit (the housing center itself).
“The word modular means that you can change the pieces on a base unit to come up with a different configuration, and that’s the idea behind the modular housing,” explains Mark Williams.
Mark Williams’ standard 28-7/8-inch 12-bolt housing with aluminum billet four-link brackets (18-inch centers) and aluminum end bells.
As you might expect, the 12-bolt and 9-inch housings are the most popular of the MW Modular housings. At left is a complete 12-bolt assembly with aluminum four-link brackets, aluminum end bells, 35-spline aluminum spool, Richmond Pro Gears, gun-drilled axles, and MW disc brakes. The entire assembly is 138 pounds. On the right is a 9-inch aluminum housing that can be used for drag racing or street applications. The housing has a reinforced center module cast from special grade aerospace alloy with an incredible tensile strength of 60,000 lbs.
The word modular means that you can change the pieces on a base unit to come up with a different configuration, and that’s the idea behind the modular housing. – Mark Williams
Mark Williams produces three different housing styles and a myriad of interchangeable components (which we’ll get into later in this article), creating a virtually infinite number of combinations to fit specific applications. Not only are the components easily swapped, but the Modular housing line affords the option of easily upgrading from a 9-inch to an 11-inch, using the same parts, and vice versa. The result is a system that can last you for many, many years, through any number of race cars, and can be upgraded or repaired without costly expense or fab work. But Mark Williams’ engineers have created benefits to these housings beyond just their convenience.
The Modular Advantage
“One of the reasons that we really like the modular housing is that it’s completely machined, so it eliminates some of the problems that you encounter with welded housings,” explains Williams. “The design and fabrication of welded housings can sometimes take things out of relationship to one another, but because we machine the modular housings using a horizontal axis machine center, everything is exact within very tight tolerances. The biggest thing is the accuracy of the housing.”
This precision is measured down to +/- .001-inches in all critical dimensions, which delivers great operating efficiency and the elimination of binding due to misalignment. As well, the axle and spool bearings are perfectly aligned and the pinion exactly perpendicular, therefore, less horsepower is lost in its travels to the rear wheels.
The MW Offerings And Options
Big Power: Meet MW's 11-Inch
MW’s 11-inch Modular housing was designed from scratch to offer more strength and support for high-powered racing applications than its smaller 9-inch counterpart, which is derived from the original OEM Ford 9-inch. With the 11-inch, you’re not limited by the size of the ring and pinion gear. The 11-inch bears no resemblance to any OE part, and because of its size and robust design, comes in 20-25 pounds heavier than the 9-inch, depending on the configuration. While some racers opt for the 9-inch for the weight savings, Williams points out that ring and pinion replacements are more common when doing so. Simply put, for monster race applications, MW’s 11-inch modular is the ticket.
Of course the main advantage that modular housings offer is the upgradeability and easy maintenance of being able to swap out components to fit almost any vehicle application. Want to move a housing from a dragster to a suspended doorslammer or even a street car? No problem.
“If someone wants to put our housing on a suspended car, we can put steel tubes on it for OEM-style suspension setups, or we can put four-link brackets on it that go up right next to the housing center and then we put what we call and end bell that can either be for as regular flange configuration axle or a full-floating hub,” said Williams. “So you easily go back and forth or upgrade, depending on the car and the class.”
Mark Williams’ modular offerings begin with the housings themselves, of which there are three different aluminum centers, all of through-bolt design. The first of these is the beefy 11-inch version, designed to handle the power of supercharged, turbocharged, nitrous-fed, and injected nitro cars in classes such as Top Alcohol Dragster and Funny Car and Pro Modified. These use a proprietary 11-inch diameter ring gear and companion pinion gear made by Richmond Gear and have been known to last for hundreds of runs with only basic inspection and maintenance in 3,000-4,000 horsepower machines.
Next is the popular 9-inch Ford aluminum modular, which takes the most popular housing design in drag racing to another level. This housing, like the 11-inch, uses an aerospace alloy rated to a tensile strength of 60,000 lbs. With its reinforced ribbing and the accuracy of the machined design, these housings are rock solid.
Shown here is a pair of standard end bells for the 9-inch Modular housings: one 4-3/16
Last, but certainly not least, is the 12-bolt housing. This particular housing is popular in lighter weight, lower horsepower vehicles because the GM 12-bolt design, due the ring gear size and hypoid position, and has less internal friction than a 9-inch. These are also lighter than a 9-inch by 10-15 pounds depending on component selection. MW has made a number of improvements to these housings, namely an internal cap that supports the thru-bolts that increase its reliability.
Another pair of end bells for the Modular housings: these being floater bells designed for dragsters, altereds, or Funny Cars. This view provides a look at the varying widths these can be made to fit varying applications.
Each housing has its own list of options, and as you dig into the catalog, you’ll find modular components for virtually any application. The 12-bolt housing, for example, can be had in either solid-mount or four-link, with 4130 brackets for dragsters or steel-tubed door car housings in a number of widths. The 9-inch, likewise can be solid or four-link mount, with full-floater options and four-link bracket layouts.
From there, you get into the keyed spacers, mounting brackets, end bells (used most for dragsters and altereds), four-link bracket options, and the centers themselves. And if you can’t make what you need from the options MW affords, custom modular housings with specific four-link layouts can be had.
The Modular housings use spacers like these to create the needed space between four link brackets or to widen the housing to fit a particular vehicle con configuration. You can see the male/female machining that allows the parts to fit together without placing stress on the bolts.
The housings themselves and the add-on components all use machined, matching male and female notches that fit together to provide the rotational support, so that the bolts themselves are simply holding the components together, but not bearing the brunt of the torsional stress that the housing endures.
In terms of material, all of the end bells and brackets are made of 7075 aluminum, while the housing centers are a 206 alloy casting, which is close to the same strength as 7075. At 68,000-70,000 pound tensile strength, in Williams’ words, “it’s super-strong stuff.”
The Racers That Use Them
While the modular technology has been slow to gain traction (no pun intended) in the upper echelons of the drag racing world, racers are beginning to gravitate to modular housings for the very benefits and advantages that we’ve discussed here. Williams shared with us that many of the Pro Stock and Pro Modified chassis builders are beginning to move away from welded housings to the modular, and they count some of the biggest names in the racing industry among their core customers.
Among those utilizing Mark Williams modular housings on their customer builds are Tim McAmis Race Cars, Don Ness, Jerry Bickel Race Cars, Wally Stroupe Race Cars, Pro Chassis Design, Garrett Race Cars, Neil & Parks, Spitzer Race Cars, and Sarmentos Race Cars. As well, R2B2 Race Cars has used MW 11-inch modulars on virtually every one of their Pro Modified cars, including the reigning NHRA championship-winning, twin-turbo Corvette of Troy Coughlin, the record-setting ’53 Corvette once driven by Melanie Troxel, the ’12 Mustang formerly driven by Leah Pruett and Eric Dillard, along with others.
What Mark Williams has developed with their Modular rear end housings is a simplified design of the age-old rear end housing. Sure, looking at all of the options available might seem overwhelming on the surface, but the result is a product that you can carry with you for years, amongst any number of cars and configurations. This fact, combined with the strength that these housings provide, you almost have to question why cast or welded housings are still needed. When asked if he felt that Modular housings and the advantages they provide are the way of the future, Williams replied, “It’s definitely moving that way, but I think you’ll still see both types of housings in drag racing.”