Mustang Steering Rack Tech

Threads on Tie-rods

OEM Tie-rods

• 1979-93 Mustang steering rack tie-rods, power and manual, have 9/16"-18 SAE threads. Manual racks were only available on 1979-84 Mustangs.
• 1994-04 Mustang power steering rack tie-rods have metric threads, M14x1.5

Aftermarket Manual Steering Rack Tie-rods

• Aftermarket manual steering racks are made by several companies. All have tie-rods with 9/16"-18 SAE threads for all model years, 1979-04.
• To order the correct bumpsteer kit for installation with a manual steering rack into a 1994-04 Mustang, choose from the bumpsteer kits offered for 1979-1993 Mustangs, as those have the SAE threads required to fit the SN95 manual steering rack inner tie-rods.

Steering Shaft Differences

• Until Flaming River made a significant change to the input shaft of their manual steering racks in early 2012, all manual steering racks for 1979-04 Mustangs, whether OEM or aftermarket, shared the same small round splined input shaft.
• In early 2012, Flaming River changed the groove on the input shaft that retains the steering shaft bolt. That required a design change to the MM steering shafts for manual racks. The new design MM steering shafts are part numbers MMST-12.1 and MMST-15.1. The new MM manual steering shafts fit both the old and the new Flaming River manual racks.
• 1979-93 Mustang power steering racks use a large round splined input shaft.
• 1994-04 Mustang power steering racks use a unique Ford triangular-shaped input shaft.
• Steering shafts cannot be interchanged between power racks and manual racks because of the different rack input shafts.
• Steering shafts cannot be interchanged between the Fox generation (1979-93) and the SN95 generation (1994-2004) Mustangs because of other differences between the two different chassis.
• MM designed and manufactures steering shafts for all 1979-04 Mustang applications.
• MM Manual Rack Installation Kits include steering shafts.

Steering Rack Ratio

• This refers to the ratio of steering wheel rotational angle to the front tire steering angle.
• Standard ratio is 20:1. This means that for every 20 degrees of rotation of the steering wheel, the front tires will steer 1 degree.
• Quick ratio is 15:1. This means that for every 15 degrees of rotation of the steering wheel, the front tires will steer 1 degree.
• For a given turning radius, the standard ratio rack will require more rotation of the steering wheel than will a quick ratio rack.
• More rotation of the steering wheel means the steering feels "slower".
• Standard ratio rack requires less effort to steer than a quick ratio rack because it has more leverage; 20:1 instead of 15:1.
• Standard ratio rack requires more turns of the steering wheel, from lock to lock, than a quick ratio rack.
• In reality, the ratio is a theoretical average. The actual ratio varies slightly as the steering wheel is turned because the leverage applied by the tie-rod to the steering arm on the spindle changes, as the angle of the steering arm changes, relative to the rack. This difference in the actual ratio has no significant consequences.

Steering Rack Mounting Bushings

• Manual racks use the same bushings as a power steering rack. The bushings must be chosen to suit the year (for a stock k-member), or the brand (for an aftermarket k-member).
• 1979-84 Mustangs have 14MM bolts securing the steering rack to the k-member.
• Mustangs built from model year 1985 (10/1/84) through 2004 have 12MM bolts securing the steering rack to the k-member.
• Urethane bushings and solid bushings are available for most applications.
• Manual rack mounted to an MM K-member require spacers with 5.0 liter engines.