Have been having intermittent problem with late upshifts. First noticed no 3-4 upshift till extremely high speed. When this happens, 2-3 shift is late, can be shifted by lifting throttle above about 40MPH. Cable adjustment has some effect, but when operation becomes normal, cable seems to have normal effect on operation, that is, small movements of adjustment make corresponding changes in shift points. This problem will sometimes come and go within a driving cycle, or remain for a couple of days. When things are normal, operation is flawless-no slow or slipping shifts, even under full throttle. Anyone had this happen?? Thanks....Pat