Big Bore Xd® Steering Gear Conversion - Jeep Tj / Lj (2003-2006)

The factory Mercedes ZF box on ’03–’06 TJ/LJ Wranglers? Weak. Small piston, thin case, and a bad habit of giving up when you add bigger tires or a locker. The BIG BORE XD Conversion Gear fixes all that with a Saginaw-style box, a bigger piston for more torque, and ports for Cylinder Assist when you’re ready to step up.

This isn’t a quick swap—it’s a proper conversion. You’ll need the right hoses, maybe a little steering shaft work, and in some cases a 1" body lift for clearance. But once it’s in, you’ll have a steering gear that can handle real trail abuse without crying uncle.

Heads‑up for installers

• This is a conversion. It’s not a 30-minute swap. Plan for hoses, shaft mods, and maybe a body lift.
• Hose kit required: Use PSC HK2000 Hose Conversion Kit for a clean install.
• Intermediate shaft: Factory shaft usually needs to be shortened ~2". Or install Jeep/MOPAR PN 52078705.
• Clearance: Some rigs need a 1" body lift to clear the bigger gear and lines.
• Ports: Metric O-ring, machined for -6 AN fittings to Cylinder Assist®. No welded junk here. 
• Fluid: PSC recommends PSC 715 for best performance and component life.

What’s included

• BIG BORE XD Steering Gear (SG400R)
• Pre-machined assist ports

Not Included: Hose kit (HK2000), intermediate shaft, fluid, fittings, or body lift components.

Use it with

• PSC HK2000 Hose Conversion Kit
• PSC High-Flow Pump Kit (don’t starve the gear)
• PSC Cylinder Assist Kit (if you’re running 37s+ or hardcore trails)
• PSC Cooler and Inline Filter for system longevity

Ideal for

• TJ/LJ on 35s–40s 
• Rigs with front lockers or heavy bumpers/winch setups
• Builders planning for Cylinder Assist® down the road 
• Anyone tired of blowing up ZF boxes

Install Instructions

2003-2006 JEEP TJ steering fear upgrade - steering shaft modification tips and instructions.