My turn with the weird noise

[WadmalawJoe]

I can tell when I get close to 55 because all of a sudden I hear a very light tic tic tic noise. At first I thought it was my speedometer or its cable. The sound seemed to be coming from that area. I pulled the cable off and lubed it up good and while it was off I drove the truck to see if I would hear the noise. Sure enough I still heard the noise.
Then today I drove it into town, about 25 miles one way. Hearing the noise whenever I went 55. I was in town for about a hour or so. Then drove back and the noise was gone. It has been raining a good bit here lately. The only thing I can figure is whatever makes that noise got wet and quit making noise.
I will be driving it again tomorrow and curious to hear if the noise comes back.
I have been hearing this noise for 2-3 weeks. I had my exhaust replaced and went with a quieter stock exhaust. Now I hear noises! I thought maybe it was a exhaust manifold leak, but if I rev up the rpms while its in park it doesn't make the noise, only when in motion.

any ideas?