Hey Guys

I need some help here. I just got a 2004 T.B. I6 It seems to have a vibration or humming noise when shifting into overdrive( around 1500rpms. ) Usually it occurs about 50mph. The TB has 58k on it. I'm not sure if tranny fluid has been changed, or if it a possible tranny mount. I don't think it is wheel bearings, i had an 05tb changed those on that one but doesn't seem like the same noise. Tranny shifts fine, goes with no problem just that humming noise worried about possible problems. Fluid looks good and the level is fine. Any help with this is greatly appreciated.

Thanks