KellTrac Big Bertha Differential Bolt Kit – Rubber Bushings (KTI-HWK15RD-R) - 2015–2026 Mustang
The KellTrac Big Bertha Differential Bolt Kit is engineered for Mustang owners who refuse to rely on undersized factory or aftermarket differential mounting hardware. Designed specifically for KellTrac’s rubber differential bushing upgrade kits, this system replaces standard M14 hardware with the largest, strongest differential bolts available for the S550 and S650 platform.
High-power launches, aggressive driving, and track abuse place extreme loads on the rear differential mounts. The Big Bertha kit dramatically increases clamping force and fastener strength, helping prevent unwanted movement, hardware failure, and long-term driveline damage. With massive through-bolt hardware and precision-grade components, this kit delivers the strength and confidence demanded by serious performance builds.
Purpose-built for KellTrac full rubber differential bushing replacement kits that require longer-than-stock hardware, the Big Bertha system ensures your differential is locked firmly in place—exactly where it belongs.
Features
- Industry’s largest and strongest differential bolt kit for S550/S650 Mustangs
- High-strength alloy steel bolts with 170,000 PSI tensile strength
- Bolts are 15% larger than the next strongest offering
- Provides 25% more clamping force than comparable kits
- ASTM A574 hardware with zinc-coated Grade 8 flanged nuts
- Includes high-quality name-brand HSS drill bit
- Complete kit with bolts, nuts, washers, and required installation components
Important Notes
- Designed exclusively for KellTrac full rubber differential bushing upgrade kits
- Not compatible with factory or polyurethane differential bushings
- Drilling of all differential bushing and mount locations is required
- Minor grinding required on the front side of the rear differential cover mounts
- Recommended torque: 185 ft-lbs with a small amount of blue threadlocker
Fitment
- 2015 Ford Mustang
- 2016 Ford Mustang
- 2017 Ford Mustang
- 2018 Ford Mustang
- 2019 Ford Mustang
- 2020 Ford Mustang
- 2021 Ford Mustang
- 2022 Ford Mustang
- 2023 Ford Mustang
- 2024 Ford Mustang
- 2025 Ford Mustang
- 2026 Ford Mustang
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
