Frame Cutting and Preparation
The MB3025 requires cutting away the factory rear frame structure and welding the replacement frame rails into position. This is a fabrication-intensive installation intended for builders experienced with chassis modification, frame alignment, and suspension geometry.
Motobilt provides defined factory frame cutting locations and alignment holes to assist with positioning the replacement structure.
Use a saw to make the required frame cuts. Do not use a torch for cutting the factory frame at the specified installation locations.
Frame Layout and Suspension Packaging
The replacement frame rails are positioned 5" inward per side above the rear axle centerline to create additional clearance for coilover shock packaging.
The rear frame is shortened 2.5" and raised 1 1/8" compared with the factory configuration. Four factory crossmembers and two factory body mounts above the axle are removed as part of the conversion.
The new frame rails include two replacement body mounts positioned to factory specifications.
Before final welding, verify frame alignment, axle position, suspension link placement, shock travel, and clearance throughout the suspension's intended range of movement.
Fuel System
The factory fuel tank must be removed to install the MB3025 back half kit. An aftermarket fuel cell is required.
Motobilt MB5013 is designed specifically for the MB3025 back half system. It includes a skid plate and is compatible with the factory fuel pump and sending unit.
Plan the fuel cell mounting, fuel lines, and related components as part of the rear chassis fabrication.
Four-Link Suspension
The MB3025 provides a replacement rear frame structure suited to four-link suspension packaging.
Motobilt offers the MB7000 and MB7001 four-link kits for Jeep JKU applications. These are related components for builders completing the rear suspension conversion.
Verify the complete suspension layout, axle-side mounting locations, driveshaft clearance, and shock positioning before final welding.
Additional Modifications
The factory exhaust must be modified to accommodate the new rear frame layout.
The MB3025 is compatible with the JK Antirock sway bar kit. Check sway bar and suspension component clearance during assembly.
The kit ships in bare steel. Complete all necessary test fitting and welding before applying paint or another suitable protective coating.
