MM News

SN95 Steering Rack Upgrade for Fox Mustangs

Why would I want to install an SN95 steering rack in my Fox Mustang?
To improve the steering feel so you can drive better and faster: i.e., more fun.

Tech Note
To get you up to speed on this important topic, here's a quick explanation of how power steering works:
  • When you're driving straight, there's no power assist; you've got manual steering.
  • When you rotate the steering wheel, it applies a load to the steering rack.
  • That load twists a small torsion bar in the rack, which rotates a valve that turns on the power assist.
  • The more torque applied to the torsion bar, the greater the amount of steering assist you get.

What's wrong with my Fox steering rack?
Compared to an SN95 steering rack, the Fox rack has a much more abrupt transition when the power assist comes on, and it gives more total assist. With a Fox rack, the steering feel changes rapidly from moderate effort to very low effort as the steering wheel rotates and the assist begins. This abrupt change often causes the driver to rotate the steering wheel further than intended at corner entry because the high level of assist makes fine steering adjustments difficult. Compared to the SN95 racks, the greater assist of the Fox racks causes a lighter steering feel. That reduces feedback to the driver, making it difficult to tell what's happening at the all-important tire contact patch.

What's different about the SN95 steering racks?
In 1994, Ford made significant changes to the steering rack, including making the torsion bar stiffer and adding a two-stage transition to the valve to activate the assist. Those alterations made for a smoother shift from no assist to power assisted, and slightly higher effort because there's less total assist. Performance driving with an SN95 rack is much more enjoyable (and possible) now because steering feel and driver feedback are better, meaning you can tell what's happening at the tire contact patch.

Note 3 more important changes to SN95 racks:
  • Externally, the input shaft changed from round with splines to a proprietary triangular shaft that mates to a matching lower steering shaft connection.
  • The SN95 inner tie-rods are longer so they match the longer SN95 front control arms.
  • The threads attaching the outer tie-rod ends to the inner tie-rods changed from standard SAE to metric.
What's the same between Fox and SN95 racks?
Fortunately, everything that makes it easy to retrofit an SN95 steering rack into a Fox chassis Mustang is unchanged:
  • The mounting to the bushings on the K-member is the same.
  • The connections to the hydraulic lines are the same.
  • The threads attaching the inner tie-rods to the center rack are the same.
  • The operating pressure from the hydraulic pump is the same.
What do I need to install an SN95 steering rack in my 1979-93 Mustang?
  • MM's Hybrid Steering Shaft Assembly. It has the correct lower U-joint to connect to the unique triangular input shaft of the SN95 steering racks. This engineered MM hybrid assembly also features a splined joint so you can correct steering wheel orientation. This feature is required to center the steering wheel properly with an SN95 steering rack. Without this proprietary feature of the MM Steering Shaft, the steering wheel would be rotated nearly 90 degrees from center! (Although it may seem that the un-centered position of the steering wheel could be fixed during an alignment by adjusting the left and right tie-rods in and out, that's not the case. Having the tie-rods adjusted to different lengths will cause severe asymmetric bumpsteer that cannot otherwise be corrected.) The MM Hybrid Steering Shaft does not disturb the stock steering wheel or airbag (if equipped).
  • Fox chassis inner tie-rods are required when retaining Fox chassis front control arms. The correct-length Fox inner tie-rods can easily be swapped onto an SN95 steering rack because the inner threaded connection, where the inner tie-rod attaches to the rack, is the same for both Fox and SN95 racks.
What if my Fox Mustang has SN95 front control arms?
Don't panic. You have options:
  • When using a stock outer tie-rod end rather than a bumpsteer kit, use the SN95 inner tie-rods and SN95 outer tie-rod ends, regardless of the spindles installed on the car.
  • When installing a bumpsteer kit with a steering rack that has SN95 inner tie-rods, use our MMTR-3 or MMTR-4 bumpsteer kits. The choice depends on whether you have an MM K-member (requires MMTR-3) or another brand.
  • When installing a bumpsteer kit with a steering rack that has Fox inner tie-rods, use our MMTR-6 or MMTR-7 tie-rod kit. The choice depends on whether you have an MM K-member (requires MMTR-6) or another brand.
What other parts might I want to install as long as I'm doing this whole thing?
  • MM Steering Rack Bushings are an excellent way to tighten up your steering response.
  • You can use an MM Bumpsteer Kit instead of stock outer tie-rod ends, but only if you're going to use a real bumpsteer gauge to measure and correct bumpsteer.
  • New seals to attach the hydraulic lines to the steering rack.
  • New inner tie-rods. The inner pivot joint wears out much sooner than the outer tie-rod ends. If you plan to reuse your tie-rods, make sure the inner joint has no play.
  • High-performance power steering fluid.
Are all SN95 steering racks the same?
No. There are many different SN95 steering racks.
  • All 1999-2004 Mustang racks were improved over the 1994-1998 racks with the addition of reduced-friction internal bushings.
  • In general, Cobra model steering racks have higher effort than GT model racks. GT racks have higher effort than V6 model racks.
  • Some special-model Mustangs have unique steering racks with further changes to increase effort and improve feel. Those include the 1999-2004 Cobra and the 2000 Cobra R.

How do I choose an SN95 steering rack?
Select a steering rack from the table below. It shows the original application and the corresponding SPR code, which is the key to identifying Mustang steering racks.

We've ranked the racks listed in the table with a desirability number. The lower the number, the better the steering feel for performance driving. "Best steering feel" means reasonable steering effort balanced with good driver feedback. Any of the SN95 racks are more desirable than any Fox rack, for the reasons explained above.

You'll see that our table doesn't list anything for the 1994-1998 steering racks. That's because those older SN95 racks aren't as good as the 1999-2004 racks. If you're going to the effort to swap racks, choose a 1999-2004 rack.

Finding your SPR Code
All Mustang steering racks are identified by what's called an SPR code, which is stamped into the aluminum steering rack housing in the location shown in the photo below. The code can be difficult to read, so clear it off with a wire brush to improve contrast and readability.

Note: The part number cast into the steering rack housing doesn't matter; it tells nothing about the important stuff inside. The only way to know what steering rack you have is to identify the original application for the steering rack, and that's through the stamped SPR code.

Beware of steering racks from large rebuilders. Often the SPR code is stamped over or obliterated. Even if it's visible, it should not be trusted. Most rebuilders work on steering racks in batches and pay no attention to keeping the insides of the rack matched to the housing. Rebuilt racks from the major rebuilders may not have the parts inside as indicated by the SPR code. We strongly recommend against using them.

We recommend:
  • A low-mileage steering rack from a used or salvaged car. If you can, inspect the car and ensure it wasn't hit in a way to damage the steering rack.
  • A rebuilt steering rack from a Ford dealer.
  • A rebuilt rack from a local rebuilder, if you're confident they'll do it correctly.

If you get a used rack and find it needs rebuilding due to leaks, we recommend using TurnOne Steering Systems. They have the correct equipment to rebuild and test the steering rack properly.

SPR Code ID info

SPR Code location info