The fact you claim the shift from 1-2 is "fine" seems to suggest the modulator is set way too soft. That 1-2 shift will be a little quick if you have the rest of the modulator and vacuum adjusted properly. 2-3 and 3-4 should be firm, but not jarring. If they're smooth and soft, you're destroying your transmission clutches. As mentioned in posts above, a properly tuned 722.3 should be firm, but not so firm that it feels like someone dumping the clutch. After you get it shifting nice and firm, you can soften it a bit with adjustments to the VCV, but don't go for smooth/soft or you're right back where you started. Contrary to what seems obvious, a smooth/soft/slow shift causes significantly more wear to the transmission than a quick/firm one does.