Steeda S550 Mustang Threaded Differential Through Bolt Upgrade Kit (2015-2022)

$5.00 (4%)
Steeda S550 Mustang through threaded differential bolt upgrade kit for IRS Ford Super 8.8" differential

Part Number: 555 4051
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Suggested Mods


Upgrade your S550 Mustang IRS differential hardware with Steeda's all new through Threaded Differential Bolt Upgrade Kit. Through bolting the rear super 8.8" differential to the IRS subframe on S550 Mustangs has become a popular modification due to premature bolt failure. Rather than permanently modifying your subframe by drilling out the bushings and differential housing, Steeda designed and machines in house a custom high strength hardened bolt that completely threads through the system. Post heat treatments the machined parts are nickel plated to prevent galling and provide superior corrosion protection. Using heat treated 4130 Chromoly steel, these custom bolts are as strong as a class 12.9 fastener and have been proven to last on some of the quickest and fastest S550 Mustangs out there, including Steeda's Silver Bullet.

Steeda's S550 Mustang THRU Threaded Differential Bolt Upgrade Kit is a must for all performance enthusiast looking for some bolt-in peace of mind.

Intended to be used in conjunction with our all new 555-4050 - Steeda HARDCORE S550 Mustang Differential Brackets.

Product Benefits
  • No permanent modification
  • Custom designed for this application
  • Nickel plated to prevent galling
  • Upgraded hardware over OE
  • Heat treated 4130 Chromoly for similar strength to grade 12.9 hardware

CA Residents: Cancer and Reproductive Harm WARNING

Fitment & Features


Manufacturer: Steeda Autosports

Installation Information:

Level of Difficulty: Medium
Install Time: 4 Hours
Tools Required: Basic Shop Tools
Print Instructions: Installation Instructions

Vehicle Fitment:

Fits Model Year: 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022
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