Noise at start up

[Flryder]

Hi, I have a 2012 Tradesman 4.7 4x4 @ 116,000. When it is first started from cold it has a noise that sound like "tunk tunk tunk" once it goes off of high idle. The noise is heard the loudest under the truck around the area between the front doors. The noise will disappear when you bring the RPM's up and hold the RPM's steady. The noise completely disappears when the truck is fully warmed up. Here are my diagnostics so far:

Checked exhaust for looseness - all tight
Checked for loose torque converter bolts - all tight
disconnected the coils one at a time while running - no sound change at cold
removed the exhaust manifold heat shields - found no obvious manifold cracks or broken bolts

The truck runs great and smooth. I don't think it is a rod or main bearing because those get louder as the motor gets hotter. I am needing some ideas about what to do to figure this out.

Thanks,

 

[Burla]

Most likely culprit is lifters as we hear in hemi tick, try uploading a youtube from your webcam so we can hear it. Try getting a 6 dollar bottle of lubegard biotech and see if it goes away or changes in any way. Cam/lifters are seriously lacking lubrication at low idle or start up when the oil is way thick. High rpm usually brings about the end of hemi tick. You can address most hemi ticks with lubrication strategies as ram forum has proven, of course assuming it is hemi tick.

 

[daveray9]

Def sounds like an exhaust leak at the manifolds.