Truck is a 1998 F150, 4.6l. This morning at startup the OD light on the shift lever started flashing. After a couple of restarts it stayed off. Tonight it began flashing again. Went off after re starting again. Does anyone know what is going on?

 

The ecu has found a fault in your transmission. Can't tell you exactly what the problem is, but when mine did that back in January it would have been an $1800 fix if I hadn't had the extended drivetrain wty.

I'd get in in as soon as possible to prevent damaging more parts.

 

Check fluid level before you get too upset. the light will flash when the level is low and it starts to affect internal pressures. If the fluid smells bad have it serviced ( with a filter... Not the speedy lube drain and refill ) Always start with the basics and you will sometimes save yourself a lot of time, money and worry.