2007 Dodge 6.7L exhaust brake squeal?

Similar post on the Cummins forum.

Hope this helps you some. I read this forum often and it helps a lot with our trucks.

Yes, that is exactly the noise a cracked or leaking manifold will make unless it has a major hole. Then the noise will be more throaty - I doubt that's the case because you'd see high EGT's and low boost with smoke. It wont back-fire.
You cannot crack the manifold with your driving style. It will down shift on its own if it really needs to. And stock tuning wont allow for that anyway because of the later timing (EGT may seem high but doesn't stay in the cyl long enough to be a problem).
With a lot of very heavy towing in the hills the manifold may eventually shrink - this is less of a problem on the 6.7 than the 5.9. You can see this by the mounting bolts being bent inward toward the center of the manifold. If this gets bad enough it will break either the ears of the manifold or the bolts.

EDIT, wanted to add that you may see tell-tale black soot marks where any leak is too.

EB itself works great. Just got back from a 500 mile trip with numerous long steep downhill grades. Some have stated that the 6.7L EGT's run hot and if I am not down shifting enough on hills then its possible the high EGT's would crack or warp the exhaust manifold.

On a gasser an exhaust manifold leak causes deep drone sounds or backfiring. On a diesel with exhaust brake a leak would cause a high pitched squeal? No such noise if EB is off or otherwise disengaged.

THe OP's exhaust brake is built into the VGT so no butterfly.
My first though would be a leak in the exhaust manifold someplace.

I would take a bottle of soapy water (windex will work) and after starting the eng cold, quickly spray all around the manifold before it warms up to much. The bubbles will show you where the leak is.

Is the EB loosing efficency? Time for a turbo cleaning I suspect

maybe time to service the exhaust valve. the "butterfly valve" sounds like it might be closing completely, the valves are designed not to close completely to prevent them from sticking. the valve does have orifices in the plate, to allow exhaust gases to pass when exhaust brake is actuated. could be that the valve is dirty and the whistling your hearing is the exhaust gases passing through a much smaller orifice. or the actuator piston needs calibration...over extending causing the butterfly valve to close completely.

In for info.