01 ranger tranny

Truck has 2.3 I4 automatic od trans. Delayed hard shifts 1st to 2nd, only every so often. This also happens sometimes when slowing almost to a stop then accelerating, again only every so often not all the time. Has been doing this for a few months so I dropped the pan and everything was clean and no bad smell but still has the same problem.

Any thoughts ?

Forgot to mention that filter was replaced when pan was off.

You may consider using something like Auto-Rx. If there’s something stuck, it will remove anything hanging up the internals. Google it. It did wonders for my jeep’s trans. It worked normally, but would hang up as though I was at WOT and shift only at governor limits every once and a while. Your trans is probably more complicated, but it also smoothed stuff out in my daughters college beater, a 93 Taurus. It would slightly hang up in the return to 1st when slowing and the transitions on the up shifts were more abrupt pre-treatment.