I'm not sure if you have an auto or manual trans but I remember years ago I had a similar ticking noise with my car that drove me crazy. The noise would come and go as the engine temp would change. Ended up being a hair line crack between the flexplate bolt holes. The flexplates are known to crack there. It was so small to see but if I tapped the flexplate with a hammer you could hear the difference in sound near the crack.
