Product Description
Upgrade the steering strength and control of your Jeep with the PSC SG400R Big Bore XD Cylinder Assist Steering Gearbox. Designed specifically for the 2003-2006 Jeep Wrangler TJ and LJ platforms, this heavy-duty steering gearbox replaces the weak factory Mercedes ZF unit with a much stronger Saginaw-style steering gear engineered for extreme off-road use. The SG400R features a larger piston diameter to dramatically increase steering torque output—allowing your Jeep to easily turn oversized tires and handle the added stress of lockers and aggressive off-road terrain. This gearbox is machined with integrated -6AN cylinder assist ports, making it the perfect foundation for hydraulic assist steering systems commonly used in rock crawling and trail builds. Built with billet aluminum covers and reinforced internal components, the PSC SG400R delivers exceptional durability, improved steering feel, and the strength required for extreme off-road conditions. Whether you're upgrading for 35"+ tires, hydraulic assist, or serious trail use, this gearbox is one of the most trusted steering upgrades in the Jeep off-road community.
Fitment
- 2003 Jeep Wrangler TJ
- 2004 Jeep Wrangler TJ
- 2005 Jeep Wrangler TJ
- 2006 Jeep Wrangler TJ
- 2004 Jeep Wrangler LJ (Unlimited)
- 2005 Jeep Wrangler LJ (Unlimited)
- 2006 Jeep Wrangler LJ (Unlimited)
Designed as a replacement for the factory Mercedes ZF steering gear used in 2003-2006 TJ/LJ models. The PSC Big Bore XD gearbox converts the system to a stronger Saginaw-style steering design with significantly improved torque output and durability. :contentReference[oaicite:1]{index=1}
Specifications for psc SG400R
| Specification | Details |
|---|---|
| Manufacturer | PSC Steering Components |
| Part Number | SG400R |
| Steering Gear Type | Big Bore XD Saginaw Style Steering Gearbox |
| Turning Ratio | 14:1 Ratio (Approx. 3.25 Turns Lock-to-Lock) |
| Input Shaft | 3/4" – 30 Spline |
| Cylinder Assist Ports | Integrated -6AN Ports |
| UPC | 687927176089 |
| GTIN | 687927176089 |
| Shipping Info | Calculated at Checkout |
| Prop 65 | WARNING: Cancer and Reproductive Harm – https://www.P65Warnings.ca.gov |
Frequently Asked Questions
What does the PSC SG400R steering gearbox upgrade fix?
The SG400R replaces the weak factory Mercedes ZF steering box used in 2003-2006 Jeep TJ/LJ models with a much stronger Saginaw-style gearbox designed for larger tires and off-road use.
Does this gearbox support hydraulic steering assist?
Yes. The PSC SG400R includes machined -6AN ports specifically designed for installing a hydraulic steering assist cylinder.
Is this a direct bolt-in replacement?
This gearbox installs in the factory location but converts the vehicle to a Saginaw style steering box. Some installations may require minor steering shaft adjustments or additional components.
What tire size is this steering box designed for?
The SG400R is commonly used on Jeeps running 35" to 40"+ tires, especially when lockers and aggressive off-road driving place additional stress on the steering system.
Do I need additional parts to complete installation?
PSC recommends appropriate pressure and return hose assemblies as well as high-performance power steering fluid to ensure optimal performance of the steering system.
