Hi all,
Looking for some help in narrowing down an annoying ticking sound. The motor is in a 2003 GMC Sonoma it has 151,000 miles and has 1K miles on a fresh oil change(Valvoline High Mileage 5w30). I started hearing a rattling/ticking sound several weeks ago and thought it was my belt tensioner. I have replaced the belt and tensioner and the problem continued, so I took the belt back off and ran it without the belt and the same noise can still be heard, with the belt off I could isolate the sound to the rear of the motor.

Here some details to help.
Oil pressure seems to be normal.
On a cold start, the noise is not detectable or very mild if it can be heard.
Gets louder as the vehicle gets warmer.
intensity increases as rpms increase, at shift it seems to get a little quicker and louder. IT is the loudest in 1st and 2nd gear, quites down in 3rd to 4th, and barely noticeable at high-speed cruising.
The computer is showing no codes so seems Knock sensor is fine and not detecting knock or pinging.
I have no leaks or other causes of lost fluids, no loss of power or other performance issues, starts easily, idles and accelerates smoothly.

Any help is apreciated.