Dear Paul, do the second generation Toyota Prados (J90 1996-2002) have a unique problem of failing ball joints which leads to collapse of the front wheels?
Catastrophic failure of front wheel hub lower ball joints is not a unique Toyota Prado problem. This problem happens to other trucks or sports utility vehicles (SUVs) whose suspension design is the same. There are reasons why the lower ball joint can fail and lead to an accident.
A ball joint is a spherical bearing in a socket which works like a human hip ball and socket design. Ball joints work as pivot points which connect suspension control arms to steering knuckles or the wheel hubs. On the J90 Toyota Prado suspension geometry, the lower ball joint takes a bigger compression load as opposed to the older suspension design where the torsion bars help to redistribute the wheel hub load so it does not entirely rest on the lower ball joint. On the newer SUVs and trucks, Toyota inclusive, the coil spring, strut and upper control arms all help to carry the load of the wheel hub relieving the lower ball joint as a natural fail safe system. Ordinarily, a good genuine Original Equipment Manufacturer (OEM) lower ball joint will be able to carry the load of a wheel hub.
However, when the ball joint wears out due to age and stress of bad roads, it’s failure means the wheel hub may collapse as the ball joint has unsupported load bearing. You can avoid this situation by not ignoring the symptoms of ball joint failure which include: steering clunking noise, excessive vibration and steering wandering.
Regularly inspect the ball joints especially if your Prado J90 is a work horse or driven on bad suburban roads. Replace the bad ball joints with genuine new OEM parts from an authorized Toyota parts shop. A lot of the responsibility to prevent catastrophic ball joint failure lies on their regular maintenance with genuine parts.