I recently had my D at a friend who's a mechanic to do 'what's necessary' to get another 5 years out of it. I have 107K on it and have been running mobile one every 5000-7500 miles. It needed upper ball joints, intermediate steering shaft (#2), and a tranny service. It actually needed more, but he felt it's not money well spent due to this unidentified noise. So, I get a loud 'turbine' noise that my mechanic says sounds like it's the convertor. He had it up on the lift running and was under the vehicle to try to locate the noise. It's pretty loud, because it can be heard very clearly over the Dynomax exhaust. It's present in Park, drive & reverse, and changes with RPM. From what I've read, if there's anything going on in the tranny, it should throw a code??? Which there aren't any. It's not slipping, 4x4 works fine and it runs strong. I haven't taken the serpentine belt off to see if it's a pulley/accessory, but the noise does go away after about 15-20 minutes of driving. I've tried to search to see if anyone else has had a similar issue, but no success. Any guidance or input would be great. If I can figure this out, I have some more work to be done and hope I'm not close to putting her in the junk yard.