How a Defender Steering Box Is Rebuilt

How a Defender Steering Box Is Rebuilt

The Land Rover Defender Steering Box is a recirculating-ball unit. While generally robust, eventually the wear will catch up with the steering, and no amount of adjustment will bring it back to life. Here’s how a proper rebuild is done from strip-down to test.

Strip-Down and Fault Assessment

First, the entire box is disassembled on the bench in the correct order from new. All the parts are then laid out in front of you to see the damage for what it is before you start cleaning etc. The initial check for obvious damage, corrosion and oil contamination etc.

Identifying Worn Components

The worm gear and sector shaft are examined for signs of pitting, scoring and wear to the contact surfaces. The seals and O-rings are also removed and replaced as a matter of course. A Land Rover Defender Steering Box that has covered high miles is likely to show considerable wear on the bearing surfaces of the worm gear. This type of wear is what gives the steering a vague, ‘wandering’ feel. Understanding how the various components of the steering affect the handling of the vehicle it is attached to, it is possible to see why even relatively minor wear of individual components can cause significant problems.

Cleaning and Housing Inspection

After disassembling the box all the metal parts are thoroughly cleaned. This is also the time to check the aluminium box for any cracks, worn or stripped threads or signs of corrosion. Any damage to the threads will also need to be repaired at this stage before reassembling the steering box.

Fitting Replacement Parts

Replaced with new seals, bearings and a new worm gear or sector shaft as necessary. All parts are specified to original Land Rover Defender Steering Box part numbers in order to maintain precise tolerances and correct clearances.

Pre-Load and Backlash Adjustment

Pre-load and Backlash Adjustment: This is the most critical part of the rebuild. First the pre-load of the worm bearing must be set. This is the resistance to axial movement of the worm gear. The backlash (clearance between worm and sector shaft) must then be set. This is done by adjusting the screw on the sector shaft adjuster until the resistance through the centre of travel is firm but not tight.

Bench Testing Before Refitting

The unit is then put through a number of checks on the workbench before it is ever put back onto the vehicle. These checks include looking for smooth rotation of the two halves of the box, correct amount of resistance through the centre of travel and no tight spots or leaks.

A good quality rebuild will return your vehicle to original handling characteristics, saving you the cost of a new box.