Back Half Frame Kit for Jeep YJ

The factory Jeep YJ frame is designed around the original rear axle location. It uses a raised section over the axle to allow upward suspension travel, then drops down behind the axle toward the rear bumper. This works in a stock configuration, but it becomes a limitation once suspension travel increases or the axle position changes.

When building a YJ for more capable off-road use, the rear frame quickly becomes a problem. The factory frame rails sit inside the wheel area, limit shock placement, and drop low behind the axle, reducing departure angle and usable suspension space.

The Motobilt YJ Back Half Kit replaces the rear section of the factory frame to correct these limitations. This system moves the frame rails under the rear floor and keeps them higher and more consistent from the axle rearward instead of dropping down like the factory design.

By doing this, the kit creates the space needed for proper suspension movement and shock placement while improving rear ground clearance and departure angle. The narrowed and raised frame layout provides a cleaner structure for building a more capable rear suspension system.

This is not a frame repair section. It is a rear chassis system designed for builders who need more room, better clearance, and a stronger structure than the factory frame can provide.

Like all Motobilt components, this kit was designed by builders who understand frame limitations, suspension packaging, and real off-road use.

Frequently Asked Questions

What does a back half kit do on a Jeep YJ?

A back half kit replaces the rear portion of the frame to create more space for wheelbase stretch, improve departure angle, and allow proper shock and chassis packaging for more advanced off-road builds.

Is this a factory replacement rear frame section?

No. This is not a repair section for restoring a stock frame. It is designed for custom builds where the rear chassis layout is being changed for more clearance and suspension room.

Does this allow the wheelbase to be stretched?

Yes. Like a proper back half kit, it is designed to allow the rear axle to be moved rearward without the axle bottoming into the low section of the factory frame.

Will this work with the factory gas tank?

No. This kit requires a fuel cell. The factory gas tank will not work with this rear frame layout.

Why is a back half needed when stretching wheelbase?

The factory frame only has enough up-travel clearance at the original axle location because of the raised section over the axle. Once the axle is moved rearward, it ends up under the lower portion of the factory frame. A back half fixes this by keeping the frame rails high behind the axle.

Can I run coilovers with this kit?

Yes. One of the main reasons for this kit is to create the space needed for proper coilover shock placement and rear suspension packaging.

Does this include a rear bumper?

Yes. The kit includes an integrated rear bumper with 3/4 inch thick d-ring mounts.

Is this a bolt-on part?

No. This is an advanced fabrication system that requires cutting, fitting, and welding.

Should the body be removed during installation?

No. The body should stay on the vehicle so the factory body mounts can be used to help locate the back half during installation.

Is this part of the complete Motobilt frame system?

This kit can be used as a standalone rear chassis upgrade for a Jeep YJ, and it can also be used with the Motobilt front half and mid frame components when building a full frame system.