Auto will not downshift back to 1st when stop at lights, etc.
When start in 'D' gear it will shift up to 2nd and 3rd ok but will not shift back down when stopped. Auto shifts fine if used manually, i.e. manual shift to 1st then move up to 2nd & 3rd via T-bar shifter. Shifts back down through gears manually also with no problem. Manual shift up & down through gears is smooth. The kick down rod is OK and working. If cuising in 3rd & hit the gas it drops back to 2nd no problem then shifts back up to 3rd smoothly. Same for kick down from 2nd to 1st when step on the gas, so no problem with kick down linkage/adjustment.
So, only problem is in 'D' gear and not coming back to 1st when stopped. Is this a modulator or govenor problem? How do I check?
Comments welcomed....thanks.
P.S. have already checked vacuum line frominlet maniflod to rear of modulator valve in back of transmission. No splits, etc and is connected properly. Also, auto is full of fluid.