transmission want to go into gear while at a light
77 ranchero want to go into gear while stopped for a light.
Have you checked the ATF level?
yes I have. Could it be the vacuum modulator?
I guess I dont understand your problem as described. You say it wants to go into gear at a light? It should already be in gear, or do you shift to neutral? I was having some trans problems with my 79. i changed the vacuum modulator ($3.00 at rock auto) and it solved the problem. Good luck.