Received this email so am doing a favour and posting here.
<font face="Verdana, Arial, Helvetica" size="2">I am not a registered user but have the answer to the above item.
The original 747's had no Body Gear Steering Disarm switch; it as operative all the time with gear down. A Northwest 747 went off the runway during TO at Tokyo Haneda in the very early 70's when the nose gear skidded on a wet and slippery runway (Haneda was notorious) probably due to applying power before being completely lined up on a rolling TO. Steering tiller inputs to correct the slide resulted in the body gear steering assisting the departure from the runway as the body gear had a lot more grip and say over which way the ship went than the nose gear.
As a result of the NTSB investigation the Disarm switch was mandated by an AD. Until the switch was fitted I think the steering had to be turned off by tripping the control circuit breaker on the overhead panel prior to take off (Can any old time 747 drivers or F/E's confirm??). The NTSB chap who headed the investigation sat in on some L1011 training I was doing at Lockheed in 74 or 75 so it must have happened in 72 or 73.
Cheers</font>