1997, 2.3L, RW, 70,000 miles: After tran is warmed up (10mins of driving), it shifts hard 1st>2nd. And, kind of hard all the way up. And, clunks kind of hard shifting back down. Doesn't do it until oil is warmed up. Super smooth until then. Also, slipping a bit in 3rd.
Took it to one trans shop: Said "Code: P1744 which means TC clutch is slipping (0-247 rpm) causing it to run higher line pressure, causing the hard shifts. Full re-build required $1500-$2700" ouch! (they didn't drop the pan)
I didn't ask them, 'Why does it only shift hard when oil is warmed up?' ... that's the 1st question here.
I drive this truck like a grandma; city driving only (see low miles for 23 yrs old)

I put in 1 can of Sea Foam ran a few hundred miles and then dropped the pan and only saw minor carbon "dirt", oil was clean, red, no smell at all, no shavings at all, nothing on the magnet. Cleaned up nicely.
Put 1 container (24 oz) of Lucas trans additive in and 1 more can of Sea Foam (1 pt); topped off w/ the spec Mercon (plus new filter).
Doesn't slip anymore (that's good!), but still shifts hard (but, again, only when it is warmed up).

I'm thinking about doing a re-do on the pan but this time more than 1 Lucas additive (like 2 or 3) plus another (1) Sea Foam, and top off w/ Mercon. ... Is there such thing as too much Lucas trans additive?
Or, should I do a total flush-out and all new fluid w/ 2-3 Lucas additives?
Or, should I skip all that and next take it to a 2nd shop? $1500+ seems high just to replace the TC clutch (I assume their talking about the lock-up clutch). That won't even require opening the tran housing up, right?. Seems like a 2nd opinion would be smart.

Any other thoughts or suggestions? Thanks!