Recently my ABS light has come on and then cleared after turning off the truck. Any indications of what is causing this? Brakes work but haven't tested the ABS feature.

 

Must be one of the sensors.
On my older Superduty that was differential sensor and it seems to be the first thing to go on those trucks.
Good scanner will pinpoint the error.

 

speedometer sometimes will bounce when the sensor in the rear goes
Could be there is dirt or mud on the inside of your rotor, and the sensor is picking it up. they are pretty sensitive to dirt.
here's what the sensor #ad
looks like on a E 450

 

Here's the one on top of the pumpkin. #ad
#ad


#ad

 

On 4x4's check integral front wheel bearing.

 

When mine acts up it's usually the rear diff sensor I just pull it wipe it clean and reinstall.