It seems to be perhaps the transmission some how? It only shows up after it has warmed up, so not right when you start up and go. When I rev with the clutch pushed in, it won't make the sound; and that's why I'm thinking transmission (maybe rear end?)

It's almost a grinding sound, but different from the flywheel at idol. I actually sounds a little like a burly intake sound, but toattaly related to the transmission IMO.

The weird thing is that I never heard it before I had a 5/16 plenum spacer installed, BUT I'm pretty sure it's not the intake I'm hearing. ( I can actually feel the sound in my shift ****)

I Have the 6 speed, with aftermarket clutch and flywheel, plus 3.9 gears.

Is it possibly a fluid issue? Should I drop the transmission, or have a mechanic check it out??

Thanks,
Andy