QA1 R903S 9in. Housing for 64-66 Mustang with QA1 4-Link

Already running one of QA1’s 4-Link Suspension Kits on your classic Mustang? The QA1 9” rear housing is the perfect upgrade to handle more horsepower, improve durability, and simplify serviceability. Designed specifically to integrate with QA1’s 4-link systems, this housing delivers strength, precision, and a true bolt-on fit.

ENHANCE YOUR EXISTING QA1 4-LINK

QA1’s fabricated 9” rear housing bolts directly to QA1’s Mustang 4-link suspension systems. It features fully formed trailing arm brackets that minimize flex under heavy loads, improving suspension response and long-term reliability. Whether you’re stepping up to more power or building a street-driven restomod, this housing provides the durability and alignment precision you need - without custom fabrication.

FEATURES & BENEFITS

• Fabricated steel center section engineered for maximum strength and rigidity
• Fully formed trailing arm brackets reduce flex under hard acceleration
• Heavy-duty 3” OD, ¼” wall axle tubes designed for high-performance builds
• 31-spline 1541H alloy axles rated for up to 650 HP; housing rated to 800 HP
• Big Ford “New Style Torino” flanges (2.5” axle offset) for easy brake compatibility
• Standard 5x4.5” bolt pattern fits a wide range of wheels
• Includes drain plug, fill plug, vent port, and jack pad for easy serviceability
• ½” x 3” wheel studs for improved fitment with alloy wheels
• Factory wheel mounting surface width for proper tire clearance - 1964–1966: 57 3/8”
• Durable semi-gloss powder coat finish resists corrosion and looks great
• Includes T-bolts, housing studs, and roller bearings for smooth operation

EASY INSTALLATION & SERVICEABILITY

QA1’s bolt-on housing design eliminates the need for cutting, welding, or additional fabrication. The integrated jack pad, fill and drain plugs, and vent port make servicing simple and clean. If you already have a QA1 4-link system, this housing bolts in place for a seamless upgrade - perfect for any street, strip, or pro-touring build.

HELPFUL SPECIFICATIONS

• Fits QA1 4-Link kits for 1964–1966 Ford Mustangs
• Factory wheel mounting surface: 57 3/8”
• Big Ford “New Style Torino” flanges with 2.5” axle offset
• 5x4.5” bolt pattern (standard Ford fitment)
• ½” x 3” wheel studs
• 2.770” hub diameter
• Requires third member for Ford 9” housings with 31-spline axles

Specifications

• Axle Shaft Splines: 31
• Width at wheel mount surfaces: 57 3/8in
• Brake Flange: Big Ford "New Style Torino"
• Brake Offset: 2.5"
• Bolt Pattern: 5x4.5 in