Our 2008 cruise is giving us fits. When the vehicle descends a hill and the cruise attempts to keep the speed constant, the tranny shifts into 1st and the engine revs over 4000 rpms. Should the brakes be applied automatically to keep the speed constant or is the tranny supposed to downshift? When the tranny downshifts, it locks up and will not shift out of 1st until I come to a complete stop. The dealer thinks this is normal...I don't think so!!!

Help??