While towing a small boat my 98 v6 1500 start making this mysterious tapping noise. It's coming from the engine however at idle is silent. Now not towing this tapping has remained. It generally picks up above 40 mph and is then noticeable. The truck has about 155000 miles. I recorded a short video on the highway to give you guys a better idea. The tapping is more subtle and doesn't sound like knocking. More of a mechanical tapping if that makes sense. Any help would be appreciated.
YouTube video link
https://youtube.com/watch?v=o2uPJJJYr4I

 

I really couldn't hear anything......

 

It is the constant ticking noise sounds like a fast fowarded clock hand ticking. I've listened to it on my phone and with ear buds, i guess try turing it up more. Later on I'll post one going below and above 40 for comparison.
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here is another video where i let off the gas(no ticking) then back on (ticking starts back up)

​​​​​​https://m.youtube.com/watch?v=NflxLMWX6K4

 

bahhhh

 

Sounds like an exhaust leak... Or a zip tie in the fan... Or a possible lifter tick.
Check the exhaust manifold closely for any sings of leakage.

 

UPDATE****
Thanks frank you nailed it. Driver side manifold was leaking. Fixed it and she's back

 

Glad you found it.