4WD Manual & Automatic Transmission Conversion Kits

Toughen your truck or SUV with our PerfectFit™ 4WD Overdrive Transmission Kits. Whether you need the heavy-duty rock crawling capabilities of the TREMEC TR-4050 5-Speed or the smooth, reliable performance of our Silver Sport Transmissions' A41 4L60E-based automatic, we provide the most complete conversion systems available for 4x4 enthusiasts.

Heavy-Duty Off-Road Performance

• Rugged Versatility: Choose between the ultra-low 6.16 first gear of the TR-4050 or the highway-friendly overdrive of our 4L60E-based A41 automatic.
• Complete 4WD Integration: Our kits are engineered to work with your existing transfer case, providing a seamless fit for classic Jeeps, Broncos, and trucks.
• Superior Strength: Every component is selected to handle high-torque off-road use and increased towing demands.
• The Full Solution: We include the mounts, hardware, and technical support—no hidden costs or missing parts.

SST is proud to offer the most comprehensive 4WD conversion kits on the market. From TREMEC manuals to 4L60E-based automatics, we ensure your 4x4 is ready for both the trail and the highway.