I don't know if what I have is manifold tick. Is that a steady 'tick, tick, tick' noise? What I have is an irregular tick that seems to happen 30 seconds to 2 minutes appart. It seems to happen more when the engine is cold. I hear at idle when I first start the truck. It may or may not be happening at highway speeds, but I can't hear it over the engine. My first thought was that is was some valve or switch moving, but I've seen several posts about manifold tick and wondered if I had it. Hence the question: what is manifold tick, and what does it sound like?
Just for good measure i had the same problem w/ my ram and took it in thinking it was that or a intake gasket. 300.00$ later and found out that it was the cover that goes over the flywheel. you may have to remove the starter to get to the top bolts but that's what mine ended up being and yours sounds like my problem to the "t". the very top of the cover was being rubbed by the flywheel. you'll know if it is cause you'll see wear marks when you pull the cover. It's a horrific sounding sound too. couldn't stand it! good luck to ya!
I do hear the AC kick on/off, but this isn't that (at least I don't think it is). What I need to do, is get a Stethoscope and spend an hour tracking down the noise. But between work and beer, its hard to find the time.
slide under your rig and listen rite where your starter is while your truck is running maybe even put your hand on the flywheel cover. I'm thinkin that's what it is. your desciption is the same as mine was