Defective CVT. Only course of action is to replace the CVT.
Has he also put in new NS-2 CVT fluid? If he reused the old CVT fluid, that's not good. 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 the unique frictional properties required 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 have the unique frictional properties required for 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.So my friend has a 2010 Nissan Sentra and the trans is whining and only shifts gears when he lets off the gas. He has changed the trans filer and would like to know if there is anything g else he could do to help this problem?