Depends on the tranny ,, old tranny’s had big clearances and no electronic components ,, I’d flush and fill those..
Newer transmissions have electronic actuators and much tighter fitting parts... They are difficult to flush... Best advice is not to abuse them.. overheated fluid will cause deposits and make plungers and actuators to stick. I have resolved serious problems with 4 newer auto’s with autorx.com ,, a very slow acting and safe cleaner that dissolves varnishes. A Taurus with 150k that broke completely out of gear in U-Turns (1st gear , high load) , a Mercedes that was very slow to shift until it warmed up and the fluid thinned.. a GM 4L30 that took ages to change from forward to reverse... and a Honds Civic with 400k+ miles that was simply screwing up in multiple ways... if it’s a sticking, gummed up issue and not failed parts autorx.com will usually fix it.
If it is broken parts .. good luck , most transmission shops are pretty spotty on their quality ,, I’d almost prefer a junkyard transmission to a rebuilt.
it’s AUTO-RX.COM ,, need the hyphen , great stuff..