transmision shift selonoid on 1997 Buick LeSabre

trouble code p0740 p0753 p0758 will not downshift to first automatic or go into overdrive. can manualy put in first to take off then shift to drive and trany will shift but not to overdrive. where are the shift selonids and what is required to replace them

Asked by for the 1997 Buick LeSabre