How to Convert a Jeep YJ to LJ Length
A Jeep YJ to LJ conversion is the process of stretching the wheelbase and body of a YJ to match LJ-length proportions. This is commonly done to improve stability, create room for larger tires, and build a more functional suspension and chassis layout.
The problem is the factory YJ frame, body, and wheel openings were never designed for that kind of stretch. Once you move the axle rearward, the frame, body, rocker area, and inner structure all need to match. A proper YJ to LJ conversion is not just cutting and guessing. The chassis, body, and wheel opening location all need to work together.
Why the Factory YJ Layout Becomes a Problem
The factory YJ rear frame limits axle placement and suspension packaging. Once you start building around larger tires, long-travel suspension, and more wheelbase, the stock body and frame layout stop working together.
- The rear axle cannot move back far enough without frame modification
- The wheel opening no longer matches the new axle position
- The rocker area is too short once the body is stretched
- The floor and inner structure need to be extended to tie the system together
The Correct Way to Convert a YJ to LJ Length
Motobilt offers a complete group of components designed to work together for a 15 inch YJ stretch. Instead of piecing together random fabrication parts, this approach gives builders a repeatable way to stretch the frame, body, and wheel openings so the Jeep goes together correctly.
This Product System Is Built Around a 15 Inch Stretch
Motobilt’s 15 inch stretch products are designed to work together to convert a Jeep YJ to LJ-length proportions. That includes the rear frame, corner armor, rocker guards, floor panel, inner fenders, and tailgate support components. :contentReference[oaicite:1]{index=1}
Required Components for a YJ to LJ Conversion
To properly convert a Jeep YJ to LJ-length wheelbase, the following components are required:
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Rear Back Half Kit
MB3067 - 15" Stretch Back Half Frame Kit for Jeep YJ -
Stretch Corner Armor
MB1176 - 15" Stretch Corners w/ High Line for Jeep YJ
MB1170 - 15" Stretch Over the Rail Corner Armor for Jeep YJ
MB1170-A - Aluminum 15" Stretch Over the Rail Corner Armor for Jeep YJ
MB1175 - 15" Blank Stretch Corners for Jeep YJ -
15 Inch Stretch Rocker Guards
MB1171 - 15" Stretch Boat Side Rocker Guards for Jeep YJ
MB1171-A - Aluminum 15" Stretch Boat Side Rocker Guards for Jeep YJ
MB1177 - 15" Stretch Rockers for Jeep YJ
MB1177-S - 15" Stretch Rockers w/ Tube Step for Jeep YJ -
Floor Panel
MB1172 - 15" Stretch Floor Panel for Jeep YJ -
Inner Fenders
MB5529 - 15" Stretch Highline Rear Inner Fender Replacement for Jeep YJ -
Tailgate
MB1168 - Fold Down Aluminum Tailgate for Jeep CJ, YJ, TJ & LJ
These components work together to extend the chassis, body, rocker length, and wheel opening location to properly match a 15 inch wheelbase stretch. :contentReference[oaicite:2]{index=2}
How the System Works Together
1. Rear Frame
The MB3067 rear back half kit replaces the rear section of the factory frame so the axle can move rearward and the suspension can be packaged correctly.
2. Body Length and Wheel Opening Location
The stretch corner options extend the body and move the rear wheel opening or give the builder the blank panel needed to place it correctly. This is what makes the body match the new axle location.
3. Rocker Area
Stretch rocker guards extend the center section of the body so the front of the tub ties into the new rear section. Without stretching the rocker area, the body and armor do not line up correctly.
4. Floor and Inner Structure
The floor panel and inner fenders finish the inside of the stretch, support the body conversion, and help create the clearance needed for suspension packaging.
5. Rear Body Completion
The fold-down tailgate finishes the rear opening after the stretch and gives the builder a clean solution that works with the new body layout.
Which Stretch Corner Should I Choose?
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MB1176
Best for builders who want a 15 inch stretch corner with the factory upper rail left exposed. -
MB1170
Steel over-the-rail version for a more finished look, more protection, and integrated tail light cutouts. -
MB1170-A
Same over-the-rail design in aluminum for reduced weight. -
MB1175
Blank version for builders who want to customize wheel opening location and wheelbase.
Which Stretch Rocker Should I Choose?
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MB1177
Standard 15 inch stretch rocker for builders who want a straight rocker profile. -
MB1177-S
Stretch rocker with integrated tube step for added side protection and easier entry. -
MB1171
Steel boat-side rocker for improved clearance on obstacle-heavy builds. -
MB1171-A
Aluminum boat-side rocker for reduced weight with the same stretched fitment.
Builder Example
See how Motobilt used this type of stretched YJ system on El Jefe.
Common Questions
How much does a YJ need to be stretched to match LJ length?
Motobilt’s YJ-to-LJ system is built around a 15 inch stretch, with matching components for the frame, body, rocker area, and inner structure. :contentReference[oaicite:3]{index=3}
Can I just move the rear axle back without changing the body?
No. The wheel opening, body length, rocker area, and floor all need to match the new axle position for the build to fit and function correctly.
Is this a bolt-on conversion?
No. This is a fabrication-based system, but the Motobilt components are designed to work together so the conversion is repeatable and easier to plan.
What is the best starting point?
Start with the MB3067 rear back half kit, then choose your corner style, rocker style, and the matching support components to complete the conversion.
Shop the Full YJ to LJ Conversion System
Shop Rear Back Half Kit
Shop YJ Unlimited Stretch Components
Shop YJ Frame Systems
Shop YJ Sheet Metal Parts
Shop Rocker Guards
Shop Tailgates