I know its almost impossible to diagnose properly from an explanation only, especially from someone who doesn't know anything. But I'd like to try and track it down and could use some help from some simple auto logic I suppose.

Its clearly a tick, not a tap or knock. It only happens under load, in gear (drive or reverse) and after warming up.

I thought it might be a cat, but it doesn't tick in park or neutral when revved and warmed (at least not today when I tried to make it tick) so I assume it isn't the cat?

I'm sure there are endless possibilities, like lifters, exhaust leaks, etc. I guess I'd just like a list of possibilities so I can start somewhere or be told where to look.

Thanks.

(It's the '97)

 

Make sure your exhaust manifolds arent leaking or cracked. My truck does that every once in a while and I tighten down my manifold bolts where the down pipe bolts to the manifold and it usually cures it for a couple months.

 

Also tighten the hardware at the y-pipe flange.........