Tranny lag when hot

My transmision started lagging between gears a few thousand miles ago, so i replaced the tranny fluid. The problem got fixed and the old fluid was in pretty bad shape, there were very little metal shavings in the filter and the magnet so i assumed tranny discs were good but fluid was bad. ok, now i'm having the same trouble only when the car warms up, i'm assuming i only removed maybe half of the tranny fluid and now the new fuid mixed with the old one and it doest lubricate good when it's hot. Am i making a good guess or the car migh need a new tranny, miles are 170K never had problems with it.

I had the same problem with my 93 Crown vic. It would buck only in the summer when the car was hot. When you have metal fragments in your fluid, you should never change the fluid. The tranny is going and will need replacement.

I just got rid of it and bought a 98 Crown Vic.

what year?