My altima is making a grinding sound under the hood when I accelerate. It also makes the sound when I start the car up in the morning and it's idle. The more gas I give it, the louder the grind. I thought it was my brakes but when I got my oil changed they noticed the sound appears to be under the hood and in the tranny. The tech mentioned it was the cvt tranny and that it could be low on tranny fluid causing the inner parts to grind. It sounds like straight metal on metal but with a high pitched sound. The car is NOT under warranty. Any help or direction would be very appreciated. Thank you for your time.