Back Half Frame Kit for Jeep TJ Motobilt

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MB3008

Back Half Frame Kit for Jeep TJ

Name: Back Half Frame Kit for Jeep TJ
Brand: Motobilt
SKU: MB3008
Price: 639.00 USD
Availability: InStock
Rating: 5.0 (1 reviews)

$639.00

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Compatible With:

Product variants

Quantity

Rear back half frame kit for Jeep TJ with integrated bumper. Creates clearance for coilover suspension and improves departure angle for off-road builds.

Assembly Instructions

The factory Jeep TJ 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 problem once the rear axle is moved to stretch the wheelbase.

When the axle is relocated rearward, it is no longer positioned under the raised portion of the frame. Instead, it sits under the lower section of the frame rails. In this position, the axle will contact the frame during compression, limiting up travel and preventing the suspension from working correctly.

The Motobilt TJ Back Half Kit replaces the rear section of the frame to correct this geometry. Instead of dropping down behind the axle, the new frame rails stay high and consistent from the axle rearward all the way to the rear bumper.

This allows the rear axle to be moved backward to stretch the wheelbase while still maintaining proper suspension up travel without increasing ride height. The result is a more stable chassis with better suspension performance and improved capability on the trail.

In addition to correcting the frame geometry, the kit narrows and repositions the frame rails under the rear floor. This creates the space needed for coilovers, bypass shocks, or ORI struts while improving departure angle and rear ground clearance.

The integrated rear bumper is positioned higher and includes 3/4 inch thick d-ring mounts for recovery. The overall structure provides a cleaner and more functional layout for building a properly packaged rear suspension system.

This is not a factory frame repair. It is a rear chassis system designed for advanced builds where suspension layout, wheelbase, and frame geometry all need to be corrected together.

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

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Important Information

Designed for Jeep TJ
Rear frame replacement system
Not a front half or mid frame section
Allows for the wheel base to be stretched in back, while maintaing a low center of gravity build
Creates clearance for coilover, bypass, or ORI suspension systems
Includes integrated rear bumper with d-ring mounts
Requires cutting frame and rear body modification
Not compatible with factory fuel tank or stretch tank
Not compatible with factory coil spring suspension
Ships bare steel and must be coated before installation
Requires welding and fabrication

Which Rear Back Half Kit Do I Need?

This comes down to what chassis you’re starting with and whether you are stretching to an LJ length body.

If you have a Jeep TJ, run MB3008
If you have a TJ and want LJ-length stretch, run MB3020
If you have a Jeep YJ, run MB3001
If you have a YJ and want LJ-length stretch, run MB3067
If you have a Jeep LJ, run MB3020-S or MB3020-W

Product Specifications

Vehicle Fitment

Jeep TJ

Material

3/16 inch High Strength Steel Plate

D-Ring Mounts

3/4 inch Steel Plate with 1 inch hole

Width

Over 8 inches narrower than factory frame

Weight

Approximately 88 lbs

Manufactured

Made in the USA

Notes

This is an advanced fabrication system intended for builders performing rear chassis modification.
The factory frame must be cut at the beginning of the bend to allow proper fitment of the new frame rails.
The body should remain on the vehicle during installation to maintain alignment using factory body mounts.
Rear body trimming below the tailgate is required to allow the new frame rails and bumper position.
Fuel system relocation is required, typically using a fuel cell.

Frequently Asked Questions

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

A back half kit replaces the rear portion of the frame to create space to stretch the wheelbase by moving the axle rearward, improve departure angle, and allow proper mounting of coilovers and link systems.

Is this a replacement for a rusted rear frame?

No. This is not a repair section. It is designed for full chassis builds where the rear suspension and frame layout are being redesigned.

Does this allow the wheelbase to be stretched?

Yes. This kit is designed to allow the rear axle to be moved rearward while maintaining proper suspension up travel and clearance.
Why is a back half required when stretching the wheelbase?

The factory frame only provides clearance at the original axle location. Once the axle is moved back, it sits under the lower portion of the frame and will contact it during compression. A back half keeps the frame rails high so the suspension can cycle correctly.

Will this work with the factory gas tank?

No. The factory tank and stretch tank will not work with this setup. Most builders switch to a fuel cell.

Can I run factory coil springs with this kit?

No. This kit is designed for coilovers, bypass shocks, or ORI struts.

Does this include a rear bumper?

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

Do I need a body lift to install this kit?

No. A body lift is not required.

Is this a bolt-on kit?

No. This requires cutting, fitting, and welding. It is intended for experienced builders.