I recently bought this 1989 Ranger XLT 4x4. It has a 2.9 L V6, and a Mitsubishi 5 speed transmission. The guy that sold it to me said that he replaced the clutch, surfaced the flywheel, and replaced the slave cylinder and throwout bearing. The vehicle drives good, shifts good through all gears. The problem: when idling out of gear with the clutch disengaged there is this rattleing noise. Depress the clutch the noise stops, disengage the clutch the noise is back. I drained and changed the transmission fluid, put synthetic 75W90 in, no change. I pulled the inspection plug on the bell housing and I can see a new clutch pressure plate, but that is about all I can see. Any ideas would be appreciated. I guess it could be bad bearings in the transmission, but it shifts really nice, so don't know.

 

Sounds like a throw out bearing issue. Had a similar issue with an 84 camaro I owned, turned out I improperly placed the throw out bearing on the arm. It's also possible the bearing has gone bad, new doesn't always mean good.