From your description of the whining sound, it well could be a worn chain in the CVT. To enhance longevity, the CVT fluid should always be replaced every 30,000 mi. When the fluid stays in too long, the chemical properties of the fluid get compromised and it can no longer provide that cushion that's so needed between the steel belt and the cones. The fluid has two great enemies, overheated fluid is one of them caused by excessive jack-rabbit starts, pulling a heavy load, being stuck in snow trying to get out, etc. The other is shearing force generated by normal operation of the belt, which increases on hills or with a load. This gradually breaks down and shortens the long-chain molecules that cushion the belt. You can generally deduce that by looking at the fluid; if it's very dark brown and has a burnt odor, it's shot! Anybody who believes the advertising about "lifetime fluid" is doomed to a dead tranny around 100K, maybe less.My 2012 2.5s Altima has been making a hum/whine noise that gets gradually louder with speed and i need to figure this out, at very low speeds its not there, seems to kick around 30 km/h and reaches its loudest around 80km/h, car idles perfectly normal and if I leave the car in park and rev the engine it doesn't appear, the car still drivers perfectly fine but the sound is clearly coming from under the hood, it has 136 000 km on it and im trying to figure out it its a worn gasket or something or the beginning of the cvt transmission death throes, any help is greatly appreciated !
One of the first things to do is perform an CVT/TCM code readout with a portable scan tool that can read CVT codes (not all of them can). To be able to read CVT codes, download a copy of the CVTz50 app for an android smartphone and get a VeePeak VP11 adaptor for your OBD-II port (the VP11 is the cheapest ELM327 that works correctly with CVTz50, not all of them do). With that, you can read any CVT codes yourself, read the CVT temperature in realtime, and also check the CVT-A/CVT-B count for any history of overheating. If something bad did happen, at least you'll get an inkling of what it was from the past evidence by seeing that the counts are greater then zero.