I have a 1997 f-250 heavy duty with the 7.3 I have been having problems with very aggressive and hard shifting. While it is acting up the overdrive light on the shifter blinks. This problem goes away and it might be good for a month or so, But it always comes back. I have had it to a professional trans tech, He replaced a part on the side of the tranny. I thought it was fixed, But now it is acting up again. Any suggestions? Thank you.

 

Take it back.

 

It seriously could be the tranny fluid type. I replaced my pan /filter/fluid with full synthetc citgo fluid that said right on the bottle that it was compatible with mercon LV BUT i started having hard shifts hard down shifts and sometimes it seemed to slam into 3rd or 4th and felt like my rear end just hit a log. I went to the local ford dealer, got the correct motorcraft LV and drained the synthetic, filled with the LV and took it out for a drive. Guess what... 6month's later it funtions smooth as silk. no issues at all.

 

Iv'e had this truck looked at by three different shops, No permanent fix. I was told that it could be the speed sensor in the rear end. Also, I did have the transmission flushed, new filter,and fluid. a short time before this problem, So spudthegreater. May be right.

 

just get the standard motorcraft fluid, the dealer will look it up for you, red bottles 1qt type. Just pull the plug, measure out what you dropped, then put that much back into it. Really, it's the cheapest fix to try and a number of us have done this and had success. plus your actually using ford approved fluid at that point. If you had jiffy lube do it, :they use a one type fits many fluid... not the best way to go with the ford transmission.