Hi guys. So i bought a tahoe 2012 5.3 2wd recently and it has ticking noise on cold start for about 30 seconds and then when i start accelerating but stops when the car is in motion but even when in motion if i accelerate the noise comes back. Any thoughts?? Just a little background. I did injector cleaning. Spark plugs and wires changed. Oil changed. Oil pan gasket changed. But it didn’t have the ticking noise until the mechanic changed the rear main seal with the part it is attached to.

any help would be highly appreciated

 

Sounds like an exhaust manifold gasket. The ''doughnut'' ones at the pipe to manifold are a common one to leak. They make a ticking noise when you're on the gas when they leak.