The Western Australian Department of Mines and Energy has released a safety alert following a steering box shaft failure on a mine site, which resulted in steering failure and loss of operator control.
The incident involved the shearing of a ‘sector shaft’ of a steering box on a Toyota 4WD, which extends from the steering box with a male spline and is attached to the pitman arm, which is connected to the steering rods, along with the power steering hydraulics.
An incident investigation report received by Resources Safety found the following:
• Inspection of the failed steering box showed that a worn section of the shaft had been repaired by machining down the shaft and fitting a sleeve. This created a stress point on the shaft that subsequently fractured.
• The shaft failed without warning.
• Thirteen of 38 steering box units checked at the mine site were found to have lathed sector shafts with pressed sleeves installed.
• Of the 13 modified steering box units, two had fatigue failures.
The Department recommends that Toyota steering box units should be inspected and serviced by a qualified technician according to the maintenance schedule given by Toyota.
The Department also recommends that, given the possibility that these practices are used on similar components for other vehicles, similar precautions should be considered when maintaining or servicing critical steering linkage components on any vehicle.
According to the Department, further investigation by Resources Safety has found that refurbishment of steering box sector shafts for Toyota Land Cruisers has been common practice for some years.