I’m a new Scion xB owner (2011 Base) that has a whining noise and appears to be coming from transmission. It is the 4spd auto. I start to hear it around 20mph which is at its loudest, but around 45+, I don’t hear it as much. The faster I’m going, the quieter it gets. The vehicle has an excellent service history, but I don’t recall seeing any transmission service listed. It has 148,000 miles and the fluid looks like it needs to be changed. It sounds a little like a reverse gear whine, but not as terrible or loud and similar to a noise I hear on my ‘98 Ranger diff. Is this normal for these? It shifts very smooth and has no leaks.

 

Have you checked the front, driver side wheel bearing? If it overheated, grease might have leaked out. Check in or around the knuckle for signs of leakage. It might be bearing lube.

If it turns out you have a dry bearing, it's a good idea to replace both front bearings instead of just one.

 

Does the whine change when it shifts gear? That should help differentiate a transmission problem from a final drive problem

 

I have a similar whine which sounds like a transmission noise. 2011 xB RS 8.0. 140K and between 30 and 35 mph at about 1500 to 1800 rpm. If I speed up and the transmission downshifts, the noise goes away. I don't think the trans fluid has ever been changed.