I just acquired this truck from my parents with an actual 50k miles. It's a 2wd extra cab SR5. It seems fine except for an odd squeal while driving when the engine is cold. The sound isn't subtle. It is a fairly high-pitched whine or squeal that warbles slightly at the frequency of the driveshaft (I'm guessing). I can change it's tone and loudness by varying the throttle... no noise when coasting. If I start the truck and let it warm up for ~10 minutes, it doesn't make the noise at all... normally it takes 2 or 3 miles for it to quiet down.
Any ideas? It doesn't make sense to me. If it was a belt or something in the engine, it should make noise even when I'm not driving it. On the other hand I don't understand why warming up the engine would silence the drivetrain.
Thanks...