Wes Duenkel
April 23, 2019
Photos By: Damon Rivetti

Rubber bushings are squishy. They do a great job absorbing annoying vibrations, but they also allow things to move around under load. Sometimes too much for our liking. When we drive our Mustangs aggressively, the rubber bushings in the drivetrain “wind up” under load and then release that energy when the tires break traction. When this cycles back and forth between traction and slip, drivers describe this as “wheel hop.”

Aftermarket companies that cater to enthusiasts like us know that we care less about reducing vibration and more about putting the power to the ground quickly and smoothly. That’s where Steeda Autosports comes in. Their latest offering to stiffen up the connection between the differential and the rear suspension for S550-chassis Mustangs is their Steeda Mustang Differential Bushing Insert System.

Steeda’s ingenious solution doesn’t replace the factory rubber bushings, but rather surrounds the factory rubber bushings with harder polyurethane inserts. The result is a differential that’s more firmly supported without any permanent changes to the factory parts. Two sets of bushings are included (80-duromter [red] and 90-durometer [black]) so the customer can tailor the amount of differential support to their application.

In addition, the Steeda Mustang Differential Bushing Insert System installs in a couple hours and adds little to no perceptible increase in noise, vibration, or harshness.

It sounded like the right choice for us, so we headed to Gear Driven Automotive in Northridge, CA where owner Saul Gutierrez handled the install.

Gutierrez began the installation process by removing the factory-cat-back exhaust.
While removing the factory exhaust wasn’t required, it gave Gutierrez more clearance for working and photos.
Next, Gutierrez removed the Steeda IRS subframe support brackets.
After supporting the rear IRS subframe, Gutierrez removed the rear subframe bolts and lowered the rear of the IRS subframe slightly for more working room.
Gutierrez continued by removing the right rear differential mount bolt.
Gutierrez selected the black (90-durometer) rear polyurethane bushing and inserted the supplied steel sleeve into the bushing.
Using the supplied bolts and backup washers, Gutierrez installed the bushing inserts one side at a time.
Gutierrez finished the rear bushing insert installation by torqueing the supplied bolts to 129 ft-lb.
After reinstalling and tightening the rear subframe mounting bolts, Gutierrez moved his jack and supported the front of the subframe.
Then, Gutierrez removed the front subframe mounting bolts and lowered the front of the subframe slightly.
After loosening the front differential mounting bolts, Gutierrez discovered that our beefy G-Force axle stubs prevented removal of the bolts.
Since the OEM bolts aren’t used with the Steeda differential bushing inserts, Gutierrez resolved to cut the factory bolts with a reciprocating saw to facilitate their removal.
Gutierrez continued by installing the supplied (shorter) bolts through the differential mounting ear into the factory threaded bushing insert.
Next, Gutierrez inserted the supplied steel sleeves into the front bushing inserts.
Then, Gutierrez slid the bushing inserts into the front side of the IRS subframe.
After repeating the process for the other side, Gutierrez torqued the supplied bolts to 35 ft-lb and reinstalled the front subframe mount bolts. Done!

Photography by Damon Rivetti