Not sure if this the right thread but here goes. My 07 Duramax makes a
noise when shifting from 4th to 5th. It does it only under very light load[throttle pressure] at about 46 MPH. It 'appears' to be coming from the
drivers side of the engine compartment. Sounds like a heavy or thick
piece of sheet metal rattling for a short duration between the shift. Ya know,
while I'm writing this, it occurs to me that it sounds kind of like the old muffler
heat shield rattle on my 96 Suburban.
Any ideas appreciated. Thanks

07 D/A LBZ, 2WD, Black. No engine mods.
9k miles
Cognito braces very soon.

Check the heat shield on the turbo. They're sometimes misaligned when they are tightened down so that rattle at that speed.