16 exhaust issue?

[Slaetem]

Hello everyone! New guy here. First timer for everything. Purchased a 16 350 last year. Just hit 140K, truck runs great.
Issue - a few weeks back it made a squealing noise down hill 4th gear no load and just experimenting with the exhaust brake. Turn the exhaust brake off and it goes away. few days later same deal. I stop using the exhaust brake completely to research the issue, now upon semi hard accelegation it is making the same noise. ( Banshee howl?? ) not sure where the real issue is (Exhaust leak? turbo issue? exhaust brake? ) I’m considering repairing it myself.

Upon a visual inspection, I have what appears to be motor oil on the lower transmission housing and rear of the motor.

Vehicle history - original California rig, was deleted, returned to stock for California purchase mid 2021.
Any advice would be hugely appreciated!

 

[6.7Bison]

Likely an exhaust leak. The rear manifold studs are known to break. The manifold can then separate from the gasket and produce a squealing noise under higher exhaust pressure similar to what I think you are trying to describe. Can be repaired by yourself and the right parts. I swapped my exhaust manifolds with the BD ones when I replaced my turbo as a precaution. Might give you an excuse to upgrade the turbo while you have it out. Obviously could be a leak somewhere else too, but what you described has me leaning manifolds.

I will have to defer on the oil leak as I am not as familiar. I have heard that a clogged CCV box can cause oil leaks though.

 

[Slaetem]

Thank you for the info. I’ll check the studs. Assuming I should see signs of soot.

 

[6.7Bison]

In general, yes. May depend on how long it's been leaking as to how obvious the soot is. Also might be hard to see being in the valley of the engine up against the firewall. Best of luck to ya!