older mtn bike. 7spd cassette. changed rear wheel and reused old cassette. now it has funky shifting. i will be on the 4th sprocket and click it to 5th and it won't shift. click again and it will go. than a minute later it will click to 6th. new hub and old hub are same dimensions. same cassette. never ever shifted funny before i changed wheel.

I didn't know mountain bikes had STI.
Your problem sounds like excess friction in the cable housing. Check for any kinks in the cable or housing or anything that would cause friction along the full length of the cable. You may need to replace the shift cables and housings.
You could also try shooting WD40 into the shifters.

I don't think it is STI per se. OP, are you talking about trigger shifters that are attached to the brake lever? There should still be a distinct lever for each: brake, upshift, downshift. With Shimano STI, the brake and downshift (right-side) levers are combined.

You did not mention whether you adjusted the rear derailleur after re-installation. Changing the rear wheel may have slightly changed the distance between the cassette and the dropout/rear derailleur, requiring you to adjust the limit screws and cable tension.

rapidfire shifter. 91 raleigh peak. the cable housing is only about 12" on the front side and than it is 24" of exposed wire and than 12" or less of cable housing in the rear by the RD. not much housing to cause friction. i did not adjust the RD at all.

You only need a centimeter or so of housing with foreign cr@p in it, or a kink, or even a pinched ferrule, to create the kind of friction that results in the symptoms you describe.

But cable adjustment may be in order as well. When it's "settled" in a given gear on the shifter, and the corresponding cog on the cassette, does it grind/click at all when you pedal?

Before I converted it to grip-shifters and V-brakes, my old Univega hybrid had RapidFarts that said "STI" on them. Before I saw my first road brifter, I thought mine were the only kind of controls called "STI".

Sounds like cable stretching, use barrel adjusters to tighten slack.

jt is right , spacing, reset limits and then tension.