I changed rear axle on my 06 ford transit 350 van, abs light comes on when I first start the van, if I turn ignition key back to 'accessory' position & restart it goes out
The Anti-Lock Braking System (ABS) uses a controller to monitor sensors for wheel speed and brake pedal position for a condition that indicates a wheel lock.
If the computer notices any abnormal signals, or the lack of a signal from any of the sensors, it will turn the ABS light on, to alert the driver of an issue. In addition to monitoring the wheel speed sensors, the computer can turn the ABS light on for other reasons like low brake fluid levels or a blown fuse. Some ABS systems may flash the light a few times and then leave it on constantly. The number of flashes refers to a trouble code and can help you identify the issue. Refer to the vehicle repair guide or information online to determine what your ABS system is telling you when it flashes.
Get the ABS codes read. This will tell you where to start looking. Because you changed the rear axle, one or more sensors may be bad or were damaged in the process. Check all wiring for damage and repair any found.
If I recall correctly, Ford used a single sensor mounted to the top front of the rear differential. It is held in with a single bolt. Make sure the connector was plugged back in. Also, if you used the one that came with the axle, it may be bad.