so just finished fixing my fuel leaks and my batterries were dead so i charged the finally the truck started but now my tach wont work and my OD light is on went for a run and wont go into low gears anyone else have this issue before?

 

Most likely the DPC-100 TCU, it's in the firewall on the driver side where a PCM would be for a gas or Powerstroke engine.

TRANSMISSION CONTROL MODULE FORD F250 PICKUP 1991 1992 F1TF-12B565-CA W1D OEM | eBay