During the Fox platform’s 25-year span, Ford Motor Company squeezed every ounce of life from the 1979-2004 Mustang. Over that time, Ford’s engineers made subtle tweaks to improve the driving dynamics of the aging chassis architecture. To that end, the power rack-and-pinion steering gear was incrementally tweaked to improve steering feedback and performance.
Owners of early cars can benefit from this evolution by installing the steering rack from a 1994-2004 Mustang in a 1979-1993 model. The improved valving and stiffer torsion bars in the later-model racks make them a desirable upgrade that, with the help of Maximum Motorsports, is a bolt-in swap.
The magic is in the steering shaft connecting the steering column to the steering rack. While the steering rack mounting points are shared across all 1979-2004 Mustangs, the 1993-and-earlier cars’ output and input shaft styles differ from that of the 1994-up cars. Maximum Motorsports offers a “Hybrid” Solid Steering Shaft Assembly (PN MMST-13) that is compatible with the early steering column and later steering rack, so the later racks can be installed in the early cars.
The later cars utilize longer inner tie rods to accommodate the SN95’s wider track width. Fortunately, swapping shorter inner tie rods from a 1979-1993 onto the SN95 rack is all that’s required to complete the conversion.
Our test subject for this project is a 1991 GT with a leaky, worn-out steering rack. Rather than simply replace the tired unit with another of the same vintage, we decided to upgrade to an SN95 steering rack. Maximum Motorsports sent along the aforementioned steering shaft (PN MMST-13), polyurethane rack bushings (PN 6-703-BL), polyurethane tie-rod dust boots, (PN 19-1712-BL), and fresh steering rack fitting O-rings (Service-9).
We could have reused the inner and outer tie-rod ends from our existing steering rack, but the original parts were completely worn out, so we opted for fresh replacements from our local auto parts store. Finally, we contacted Delk Performance in Lebanon, Tennessee, for a salvage steering rack from a 1999-up Mustang GT. Why a salvage rack and not a remanufactured unit?
Ford specified different steering rack valve specifications for different models. While physically interchangeable, these valves feature varying boost curves to tailor the effort and feedback to the driver. Each valve style is designated an “SPR code” that is engraved on the rack. During the remanufacturing process, the valves are often mixed and matched with different rack cores, so typically the SPR code on a remanufactured rack is irrelevant. Rather than roll the dice with a remanufactured rack, the only way to ensure we got the “sportier” valving from a V8-equipped 1999-up Mustang was to get a salvage OEM steering rack.
Follow along as we show the highlights of the installation process.
Installing an SN95 steering rack into a Fox-body Mustang is a bolt-in affair with parts from Maximum Motorsports.
Here’s a list of what you need and where to get it. If your car has a bazillion hard miles on it like our 1991 GT, it’s a good idea to replace the steering pump and hoses while you’re at it.
This is the key to the conversion: Maximum Motorsports’ MMST-13 “Hybrid” Solid Steering Shaft Assembly. It connects the SN95 rack input (left end) to the Fox column output (right end).
We began by removing the outer tie-rod ends from our Mustang’s spindles. We used an air hammer and a small ball joint separator. While it works, this method can be crude, and it will damage the dust boots. We didn’t care because we planned on replacing all these parts anyway.
After draining the power steering fluid, we unbolted the rack mounts from the K-member, then after soaking the rack sleeves in penetrating oil, we pried the rack from the K-member and removed it from the car.
Note how the Fox’s power steering rack input shaft is splined (left), while the SN95’s steering rack has a unique triangular design with a slotted shaft (right).
Besides being gross, the Fox’s steering shaft (top) uses a rubber “rag joint” that dampens vibrations, but also dulls steering feel. We painted the Maximum Motorsports steering shaft (bottom) to inhibit corrosion.
We prepped the SN95 steering rack by pulling back the bellows and removing the inner tie-rod ends
Then, we installed fresh, Fox-length tie rods on the SN95 steering rack.
Our original rack bellows were cracked and damaged, so we installed fresh ones over the inner tie-rod ends.
After coating the threads with antiseize compound, we threaded on fresh outer tie rod ends.
We swapped out the rubber tie-rod end dust boots with the polyurethane parts from Maximum Motorsports.
With our SN95 rack (bottom) prepped, we laid it next to our old Fox rack (top). Using the Fox rack as a guide, we adjusted the length of the SN95 rack’s tie-rod ends until they closely matched the Fox rack. (Final alignment will be done later).
Because power steering leaks suck, we installed a fresh O-ring seal from Maximum Motorsports on the return line’s fitting.
As an added measure of leak insurance, we used the supplied thread sealant on the fittings’ threads before installing them in our rack.
Our existing power steering hose was leaky and nasty, so we installed a fresh Fox-body power steering hose onto the SN95 steering rack.
With the SN95 steering rack prepped, we slid the inner polyurethane steering rack bushings over the rack sleeves and installed the steering shaft and steering rack.
With the rack pressed over the inner bushings, we installed the outer polyurethane steering rack bushings.
Then, we installed the rack bolts and torqued them to spec.
Per Maximum Motorsports’ excellent instructions, we checked if the steering rack was centered relative to the steering wheel. We turned the rack to full lock in each direction and marked the top of the wheel with tape. We re-clocked the steering shaft until the tape marks were symmetrical on the steering wheel.
With the steering wheel centered, we installed the outer tie-rod ends.
We gave the fresh tie-rod ends a few squeezes of grease for good measure.
Our old power steering pump was (surprise, surprise) noisy and leaky, so we replaced it with a remanufactured pump.
We connected the rack return and pump feed lines to the power steering cooler loop.
With everything connected, we filled the pump with fresh fluid. While the car was still on jackstands, we bled the system by turning the steering wheel slowly from lock-to-lock and rechecked the fluid level.
Using our own string setup, we set the toe alignment measurement. Not only did we install a fresh steering system, our Fox is certainly more responsive with no drawbacks. That’s a win!
Photography by Wes Duenkel