I have tunerpro but I don't see a way to read anything other than P,Drive. Is there software that can get at the transmission codes/live data for a 1994 w 4L60E? I can't seem to get 2nd gear (slow or not at all). If I directly shift into 2nd I can get into 2nd immediately. I don't think I have 3rd or 4th.
Unplug the case connector, fire it up and put it in drive. You will be in third gear. If it moves forward, trans 3-4 pack is likely viable. If it doesnt move at all, trans has to come out for overhaul.
Check Snap On scanners as I think they are capable (with the applicable obd1 adaptor connector), of rendering live OBD1 trans and engine data. Same with a TECH1 or TECH2, I believe.
For second, check servo travel - should be between .050-0.090. If its within that range. Drop pan and air check servo (you'll have to remove valve body to air check the second gear servo piston).