KellTrac Big Bertha Differential Lockout Kit – S550 Mustang
Say goodbye to weak, failure-prone differential bushings and undersized hardware with the KellTrac Big Bertha Diff Lockout Kit—the most robust differential mounting upgrade available for your S550 Mustang. Engineered for high horsepower and high-traction builds, this kit includes everything needed to eliminate unwanted movement, reduce bushing deflection, and lock down your rear differential with unmatched strength and reliability.
Tested for over two years across numerous drag applications—including 1.1-second 60-foot launches and record-setting passes—this system has delivered zero failures to date. Whether you're chasing consistency at the track or long-term durability, Big Bertha is built to handle it.
Hardware Kit Includes:
- Industry-leading ASTM A574 alloy steel bolts (170,000 psi tensile strength)
- Zinc-coated, Grade 8 flanged nuts
- High-quality name brand HSS drill bit
- 15% larger hardware and 25% more clamp load than any other available kit
Bushing Kit Includes:
- Four 95-durometer polyurethane bushings with billet inserts
- Four oversized stainless steel washers
- Designed with zero voids for reduced deflection
- Pre-modified for perfect fit with Big Bertha hardware
Installation Notes:
- Requires drilling of bushing/mount locations to accommodate oversized hardware
- Minor grinding may be needed on the forward area of the rear differential cover mounts
- Recommended torque spec: 185 ft-lbs using name-brand blue threadlocker
If you're pushing power or chasing ETs, this is the last diff mount upgrade you’ll ever need.
Note: Most Kelltrac orders ship within 2–4 weeks. While uncommon, some orders may require up to 6–8 weeks to ship.
NOTE: Kelltrac Parts are considered Race Parts and are not eligible for ReturnCA Residents: WARNING: Cancer and Reproductive Harm www.P65Warnings.ca.gov
