2000 Jimmy Weird growling noise followed by a tick

[shesallin]

As soon as I start the truck I hear this growling that lasts about 2 sec. then stops with a "tic". This happens every 3-4 sec. It sounds like its coming from behind the dash but when I get out of the truck while its idling, it's quite loud coming from under the hood but the "tic" noise sounds like its coming from under the truck. This is happening while accelerating, breaking or idling. It doesn't ever stop. Pushed all the buttons and turned all the knobs on the dash hoping it would stop. It NEVER stops! its like a loud, growling, rhythmic occurrence and then "tic". I think its getting louder and I don't think I can take it any longer. Any thoughts on what it could be and how to go about fixing would be very much appreciated!