My guess is clearances between the pump body deck and top of the rotor and slide are way more than the .0015-.002 servicable clearance limits...Here's my
4L60E playlist where I have all sorts of videos on that trans...You can check out my
4L60E tear down and inspection video for info on forward drum pressure testing (i also think i have a short vid just showing the pressure test process). That tear down video covers all other points of inspection.
PSMA= pressure switch manifold assembly.
So you are neutral in 3rd gear (meaning it does shift from 2nd to 3rd but feels like neutral after shifting) or it doesn't upshift at all, just stays in 2nd gear I