If its making the noise in neutral then it wont be the transmission or the torque converter.

My guess is a pulley of some sort or the alternator. The bearings in the alternator can go bad without affected its charging ability so that'd be the first place i'd look.

OK. Thanks.

My next question is; how do you check the bearings in the alternator without replacing the alternator?

get a long screw driver and put the tip on the casing of the alternator. Put you ear against the other end of the screw driver and listen for any odd sounds. Otherwise if you have a second person get them to put their ear near the alternator as you rev the engine.

And oddly enough the long screwdriver method gives more clear sound then the mechanics stethoscopes available in stores... You can use that to check all the belt driven components you can get to Just be careful you don't slip the screwdriver into the running belt, for obvious reasons.

Am i wrong in thinking then that the torque converter and some of the gearbox are still spinning even when in N.

You are right in that it is still spinning, but there is no load on it so it is free spinning. If the noise is exactly the same in neutral it isn't likely the TC.

A quick way to confirm if it is a belt driven component is just to remove the belt and start it and see if the noise went away. Just don't run it for too long with the belt off obviously.

I agree about removing the belt to help find the noise. But can't agree on the TC not making noise when in N. When my TC went it made noise in gear, N, and P when the engine was revved. Had tranny rebuilt and and noise was all gone. Unfortunately my X is back in the tranny shop for the same noise/ issue after only 7 months. The rebuild is under warranty and just waiting to hear back from the shop.

Wow, the new TC only lasted 7 months? Hopefully they used an OEM 4.6is TC at least...

Were you hearing the same thing as I described? It sounds like a turbo booster or a tractor engine winding up but not necessarily loud, just annoying. It is associated with the engine RPM but once I get it up to speed and drive without the acceleration then the noise goes away until I step on the throttle again.

To my understanding they did and it delayed the rebuild by a few days as my original TC was not rebuildable. They sourced a used TC and rebuilt it. I will be paying much more attention to the details of exactly they are fixing/ rebuilding this go around.