Over the past weeks, we’ve taken a close look at fabricated (sheet metal) Ford housings. They’re absolutely trick pieces of work (and they work well by the way) but they might not be correct or best suited to all applications. You see there is one more very (very) good option available. And that’s a modular housing, available in either all-aluminum or a combination of aluminum and steel.
What’s a modular housing? It was originally engineered and developed by Mark Williams (Mark Williams Enterprises). What Williams came up with is a cast aluminum, precision CNC-machined housing center. Then, by coupling any number of different aluminum bells or steel tubes, one can create a rear end that physically bolts into a given car.
Today, Mark Williams Enterprises offers a modular 9-inch Ford floater in aluminum along with a modular 9-inch Competition Eliminator-Super Comp dragster assembly, a modular 9-inch 4-link assembly, a modular 9-inch Ford with steel tubes and steel 4-link, a 12 bolt modular Comp-Super Comp dragster housing, a modular aluminum 12 bolt with steel tubes and steel 4-link along with several other configurations. They also manufacture honking 11-inch modular setups for use in extreme power applications (think blown Funny Cars, Pro Mods, various outlaw cars and so on). Whew. But we’re not done yet. Mark Williams offers just about every piece used in their housings as separate parts. As mentioned above, the modular concept allows you to incorporate a variety of end bells and mounting brackets to suit your particular application. The reality is, there’s a huge array of parts interchange that allows you to built just about any combination from a specific width four link arrangement all the way out to a simple leaf spring package.
Of particular interest to door car drag racers are the M-W modular housings with steel axle tubes. The key element in these packages is a reinforced cast aluminum center housing module made from a special grade of aerospace aluminum alloy that is extraordinarily strong (60,000 P.S.I.). The center section is a completely machined assembly that is produced with extremely accurate precision. There is zero stress from bending and welding, typical to conventionally braced rear housings. All of the work is done on sophisticated CNC-equipment in-house at M-W. This ensures that the housing is properly aligned for optimum internal efficiency.
Two different housing designs with steel tubes are available: One is designed for use with a conventional drop-out Ford 9-inch center section while the other is arranged to accept 12 bolt GM hardware. The 12-bolt is a unique design in that it incorporates threaded carrier adjusters of the 9-inch Ford variety. This eliminates the need for spool/carrier shims. The main bearing bore in this housing is sized at 3.250-inches, which means you can use a 35 spline aluminum spool or a 40 spline steel spool. Further to this, special adjusters are optionally available to allow the use of standard 12 bolt carrier bearings with the 3.250-inch bore. In turn, this allows the use of a conventional GM-style limited slip or open differential.
The 4-link attachment points on the respective housings are the same as those used by leading pro stock chassis builders. The brackets are flame cut from 3/16” thick 1018 mild steel plate and drilled on precision CNC machines. In addition, the brackets are drilled for rod ends with a 5/8-inch hole in the ball while other mounting holes for shock and wheelie bar mounts are 3/8-inch. To further strengthen the rear end, a 1018 mild steel cross bar is used to tie the 4-link brackets to the bottom of the housing. The steel tube housings can be ordered with any 4-link center-to-center dimension as well as spring pads for a bolt-in leaf spring replacement application. You can also specify the housing end type to ensure compatibility with existing brake systems.
As far as professional style, modular axle housings are concerned the preeminent door car piece may very well be the all aluminum M-W modular 9-inch, 4-link axle assembly. In this housing, all 4 link brackets are CNC machined from 7075 billet aircraft alloy aluminum. The layout of the 4-link attachment points are again the same as those found on today’s leading pro stock cars with 18-inch, 19-inch, 20-inch and 21-inch centers available. Both floater and flange type axle configurations can be specified. Unique design features include indexing lugs on each 4-link bracket that positively lock the inner and outer brackets to each other and to the housing. This insures perfect alignment of all components and eliminates the possibility of the housing and the third member shifting between the brackets. To further strengthen the assembly, an aluminum cross tie bar is used to secure the 4-link brackets to the bottom of the housing. The housing also has provisions for either an upper or a lower wishbone attachment along with shock and wheelie bar mounts. Holes in the 4-link brackets accommodate rod ends with a 5/8-inch diameter (hole). The standard housing width is 30-7/8-inches (37-1/2-inches wheel-to-wheel) with other widths available at an extra charge.
As you can see, choices for a rear end in a racecar are almost limitless. You’re not stuck with a stock Ford or a stock 12-bolt. Better still, scrounging a wrecking yard for usable hardware is a thing of the past. And for most of us, that’s extremely attractive.