I've got a 91 Sliverado, and there's a fast paced ticking noise under my dash, it sounds like it kinda around where the shifter is it's not the fan or anything like that it changes speed with the RPM's and its there weathet im idling or running down the road as long as the truck is running its there, I can't really track it down. Any ideas on what it is?

 

Check for exhaust leaks at the manifolds and the Y pipe (or pipes, if dual exhaust).

Depending on how long it’s been there, carbon or soot may be accumulated near the source.