The overdive on/off indicator is flashing on my 99 F150, can anyone tell me what the problem is?

 

You need to go to a tranny shop and have them pull the code. Then bring it back but post the actual code in the tranny section. The tranny shop will give you a quote on a rebuilt tranny but come back before you do the rebuild.

 

Yeah you can do that and spend a bunch of money or do what they would do and replace the lock up sensor yourself so u don't get charged for a rebuild . All the ranny shop would is torque the valve body and replace the sensor.

 

There are many reasons for the OD light to flash, you do have to read out the codes.