'92 F-350 7.3. Intermitly, the O/D light will blink then the tranny will shift very hard. If you shut the truck off, the light may or may not go off. If it does the tranny will shift perfect. I changed the TPS twice, but did not help. this has been going on since 80,000 miles. The truck now has 300,000 and no one has been able to fix it. truck runs good.ran code but shows none.

 

Wonder if your having an intermittent problem with your vss sensor in the differential. It will affect the trans shift but might also give you a problem with the speedo.