The 420 and the 560 both use the 722.3 transmission which have 3 clutch packs, K1, K2 and for reverse B3. They also have two brake bands B1 & B2. The modulator can easily be adjusted without gauges if you increase it clockwise a little at a time. I would start out with one full turn and then test drive it. The kickdown issue is something totally different than modulator pressure. Check your control cable adjustment and then the electric kickdown switch under the accellerator pedal.