Hello
I have rotated in the viewport of a blueprint gears by 90 degrees and now try to make them turn but when I start the animation, they alt textturn back from the 90 to 0 degrees and then they turn in the wrong direction.
you are probably setting the wrong axis for your rotation. if in the viewport your gear was initially aligned along the x axis then rotating on the y axis would make it turn the right way, but now you rotated the gear 90 degrees so its aligned to the y axis so you will need to rotate it on the x axis.
basically plug the spin value into the x input and set the z to 90.