I'm having this really annoying issue with the extrude command. If I have grid snap on and then extrude, the Z value will always jump to a value of 0. I can't find any settings to turn it off and am currently dumbfounded.

If I try to move it on the other axis, it moves fine in increments across the grid. As soon as change to a translate tool and try to move the face on a Z axis, it also behaves appropriately. Its just a huge annoyance and I'd love to fix it if I could. Any suggestions appreciated!

Thanks!