KellTrac Big Bertha Differential Bolt Kit – Stock Bushings (KTI-HWK15RD) - 2015–2026 Mustang
The KellTrac Big Bertha Differential Bolt Kit for stock bushing applications is the ultimate hardware upgrade for S550 and S650 Mustang owners looking to eliminate weak factory fasteners without changing differential bushings. When power and traction increase, factory-size M14 bolts can flex and loosen—this kit replaces them with the largest and strongest differential mounting bolts available.
Designed specifically for Mustangs retaining factory differential bushings or aftermarket bushing kits that use stock-style bolt lengths, the Big Bertha system delivers a massive increase in strength and clamping force. The result is a more secure differential mounting solution that improves driveline stability and confidence under hard acceleration.
Featuring true through-bolt construction and premium-grade components, this kit is ideal for performance street cars and track builds that demand maximum reliability without altering bushing selection.
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, and required installation components
Important Notes
- Designed for stock differential bushings or aftermarket kits using stock-length bolts
- Not compatible with bushing kits that require longer-than-stock hardware
- 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
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