i have a '97 f-150 w/the 4.6l. Not sure of what trans is in it, but it is shifting very violently... like its trying to decided what gear to shift to. had it flushed, and then droped the pan and changed the filter... seemed fine for a couple of weeks... almost feels like a washboard when shifting... once the shift is over, it feels fine.

any ideas? thinking i may get stranded somewhere...

 

That's a 4R70W trans.

The 4R70W has an issue with torque converter shudder during shifts. If caught early enough a fluid change will often fix it. If it goes too long the torque converter is damaged and must be replaced. That's where I think yours is - ready to be replaced.