Gradient map transparency?

I am trying to create a gradient map that goes from transparent to a color. I open up a gradient map adjustment layer, click on the gradient to open up the gradient editor, click on the top left stop, set the opacity to o% and then select the bottom right stop and select red. Everything is looking fine in the editor, the left side is transparent the right side is red. I click ok, and I see that my gradient is black on the left side and red on the right. I click ok to close out the gradient map, and there is no transparency, a black to red gradient is being applied to my image. If I fill a layer with a gradient using the gradient tool, then click on the gradient to open gradient editor and do the same steps, and use the gradient tool on a new layer I can get a layer that is transparent to red, but I can't seem to get it to do the same thing with a gradient map adjustment layer?

Instead of transparent try white in the part of the gradient you want transparent.

I gave that a try and all that does is make a gradient map the goes from white to red.

AFAIK, gradient maps can not create transparency. The layer you apply the gradient map to must already have the transparency you desire.