Two problems related to steering gear box have been reported for the 1999 Ford F-150. The most recently reported issues are listed below.
Steering gear box has been replaced twice. Contacted dealer.
We could hear and feel a "clunking" through the steering wheel. Took the truck to the dealer to have it checked. Found that the lower steering shaft was broken and was advised to stop driving the vehicle until it could be repaired. Was also told by the service manager that this problem was fairly common with the f150 and in fact they had the required part to fix it in stock. This truck is only two years old and has never been driven off-road or involved in any type of accident. I am very concerned that this type of failure could occur, and apparantly is not uncommon. The break was apparantly in a "knuckle" in the steering shaft, which is why we could still steer the vehicle at all.