Edit : After a few hundred miles later it actually stopped making this noise, only slight uphill at 52 km/h I heard a faint noise. So maybe this oil needs to 'work in' (or get the old oil out).
Will post more later when I'm really sure (and drove even more miles).

 

That's the exact problem I'm having. I need to replace my Power Steering Fluid and see if that helps, though. Here is the video of the sound I'm getting when it is cold.

View My Video

 

I live in south florida and my tranny whines hot or cold. THe dealer said the tranny would need to be replaced to get rid of it, but yet my car shifts perfectly still. NOT SURE WHAT TO DO NEXT because it is very annoying when your driving a luxury car to hear that sound. Any other ideas??

 

It's getting cold again and the noise is back!
Still at the same speed, around 30 mph, or 53 km/h.
I believe it shouldn't make this kind of noise, if so what can it be??

 

Another user here in CO with the same issue. DEAD on, same speed range, same noise! I thought it was the fuel pump doing something below freezing causing an interference through the speakers. It sounds artificial to me. But I'm getting the oil changed and I will do the differential at the same time and report back.

 

I would absolutely get a second opinion on this. If I were you, I would start by just doing a pan drop and filter change. Just run a couple of quarts through, no need for a full flush. If the issue isn't solved, see if you can get a shop with an emissions station or a dyno to run the car on the rollers and make ABSOLUTELY sure it is the transmission and go from there.

 

I should have searched more for this, I am having the same exact issue, after reading this I'm assuming its relatively normal and that a fluid change could potentially solve the issue? My transmission fluid has been changed at 26k miles and diff. Fluid around 35k but that was 7 years ago and I am now at 63k miles. It was changed by the dealer so I am assuming it ws oem fluid

 

Went to valvoline and had the dif. oil changed out, would have cost $55 but i ended up paying $40. They used valvoline high performance oil i think it said. The last time the fluid had been changed was by the dealer 30k miles ago, but it was also 7 years old. The guy showed me the fluid it was pretty dark and he said a little low. I've been driving for about 2 days now with the new oil and the noise has seemed to have stopped. Temps have been within 10-25 degress F out.

 

My IS300 has begun doing this in the cold. But it starts as soon as I accelerate. Car begins to warm up it goes away. It also happens on the summer time but it is much mpre suttle. My mechanic did say the serpentine belt was cracking and it is original on an 01 with about 115k. So not being tech savy at all I will get that and the rear diff fluid changed. I am hoping it isn't tranny related. I guess I will soon find out. Thanks for some information guys.