KellTrac S550 / S650 Mustang Differential Bushing Upgrade Kit, Rubber Extreme (KTI-BUK15RD-X) - 2015-2026 Mustang
Eliminate differential movement and strengthen the rear of your S550 or S650 Mustang with the KellTrac Rubber Extreme Differential Bushing Upgrade Kit. Designed as a complete replacement for the factory differential bushings, this premium kit combines proprietary rubber and billet aluminum bushings with ultra-high-strength Italian-sourced Grade 12.9 hardware to provide exceptional clamping force, improved drivetrain stability, and industry-leading durability while maintaining the lowest NVH of any full differential bushing replacement kit.
Unlike many aftermarket solutions, the KellTrac Rubber Extreme kit is engineered as a true factory-style replacement that presses directly into the stock IRS subframe. Massive ASTM A574 Grade 12.9 fasteners generate up to 40% more clamping force than competing kits, helping eliminate differential movement during hard launches, aggressive cornering, and high-horsepower applications. The proprietary Rubber+Billet bushing design delivers outstanding performance without the excessive noise, vibration, and harshness commonly associated with solid mounts.
Features
- Complete differential bushing replacement kit for S550 and S650 Mustangs
- Proprietary Rubber+Billet bushing design
- 40% greater clamping force than competing kits
- ASTM A574 Grade 12.9 alloy steel fasteners rated at 170,000 PSI tensile strength
- High-strength Class 12 nuts
- High-quality zinc-coated HSS washers
- Includes HSS drill bit for installation
- Presses into the factory IRS subframe like OEM bushings
- Lifetime Warranty
Kit Includes
- (4) Grade 12.9 high-strength alloy steel bolts
- (4) Class 12 nuts
- (4) High-strength steel washers
- (1) High-speed steel drill bit
- (4) Proprietary Rubber+Billet differential bushings
Benefits
- Greatly reduces differential movement under load
- Improves drivetrain stability during hard launches
- Maintains significantly lower NVH than solid bushing kits
- Provides exceptional durability for high-horsepower applications
- Factory-style fit with premium billet construction
- Ideal for street, drag racing, and high-performance driving
Installation Notes
- This is a complete factory replacement kit that requires removal of the IRS subframe assembly.
- All differential mounting points and bushings must be drilled using the included drill bit.
- Torque all four fasteners to 185 ft-lbs.
- KellTrac recommends applying a small amount of quality blue thread locker during installation.
- Bushings install from the outside inward with the billet faces contacting the differential mounting ears.
- Install all bolts from the outside inward with the bolt heads and large silver washers facing outward.
- Long bolts install in the rear mounting locations, while shorter bolts install in the front.
- Front flange bushings must be installed with the arrows oriented left to right.
- Due to factory tolerances, minor shimming or differential positioning adjustments within the subframe may be required.
Fitment
- 2015 Ford Mustang GT
- 2015 Ford Mustang EcoBoost
- 2015 Ford Mustang V6
- 2016 Ford Mustang GT
- 2016 Ford Mustang EcoBoost
- 2016 Ford Mustang V6
- 2017 Ford Mustang GT
- 2017 Ford Mustang EcoBoost
- 2017 Ford Mustang V6
- 2018 Ford Mustang GT
- 2018 Ford Mustang EcoBoost
- 2019 Ford Mustang GT
- 2019 Ford Mustang EcoBoost
- 2020 Ford Mustang GT
- 2020 Ford Mustang EcoBoost
- 2021 Ford Mustang GT
- 2021 Ford Mustang EcoBoost
- 2022 Ford Mustang GT
- 2022 Ford Mustang EcoBoost
- 2023 Ford Mustang GT
- 2023 Ford Mustang EcoBoost
- 2024 Ford Mustang GT
- 2024 Ford Mustang EcoBoost
- 2024 Ford Mustang Dark Horse
- 2025 Ford Mustang GT
- 2025 Ford Mustang EcoBoost
- 2025 Ford Mustang Dark Horse
- 2026 Ford Mustang GT
- 2026 Ford Mustang EcoBoost
- 2026 Ford Mustang Dark Horse
Kelltrac Terms Of Service
Kelly considers his Kelltrac line to be a specialty line for a unique customer base and has his own terms of service in addition to Beefcake Racing's. You must accept these terms on all Kelltrac orders. Please read shipping times, cancellation, and returns. If time is of the essence, we do have other options that can ship right away / quicker. Just reach out to one of our sales associates at Beefcake Racing.
Cancellations & Returns
KellTrac Innovations does not accept product returns. Once your order ships, you own it and we will not accept it back - NO EXCEPTIONS. We do not accept order cancellations after the product has shipped. If you understand and accept this please check the box and continue checking out. If you do not accept this, please stop and discontinue the order process. Thanks!
Due to the custom nature of our business and product offerings, we charge a 20% order cancellation fee, period, non-negotiable, no matter who you are. Orders can only be cancelled before the product ships. We do not accept order cancellations after the product has shipped. If you understand and accept this please check the box and continue checking out. If you do not accept this, please stop and discontinue the order process. Thanks!
Leadtime
Please be aware that most orders ship within 2-4 weeks. In some (rare) cases, orders can take up to 6-8 weeks to ship. Holidays can severely impact these lead times. *DO NOT CONTACT US ABOUT YOUR ORDER UNLESS IT IS OLDER THAN 20 BUSINESS DAYS!* If you understand and accept this please check the box and continue checking out. If you do not accept this, please stop and discontinue the order process. Thanks!
CA Residents: WARNING: Cancer and Reproductive Harm www.P65Warnings.ca.gov
