I have a c10 auto in an XE fairmont ghia

Noticed the other day that it is not changing down gears when slowing down.

Most of the time it will take off in third and when i give it a bit it will pop back into 1st

It changes fine manually - just not in auto mode.

Another thing too is that some days it des work fine - others it doesnt

Can this have anything to do with the vaccum?

i'm also having a similar problem in my xe ute.
it starts in second.
it also shifts up at very low rpm when i drive it normally, unless i gun it.
It won't hit anywhere near redline on upshifts in D unless i manually shift it.
i think it has something to do with vacuum and kickdown cable, but i haven't got around to it

more than likely the vacume sensor on the box or a faulty hose. the cable is only if you really drop the foot.