Does anyone how to fix my 1999 F150 4.2l overdrive problem. The under hood #23 fuse keeps blowing and when , it does the truck won't shift and the overdrive indicator light flashes.

 

You don't have an "overdrive problem", you have a fuse F23 problem.

The most common cause of a blown F23 is due to wiring damage from recent maintenance or repairs, most often related to the wiring harnesses for the O2 sensors getting on the exhaust and melting.