Assuming this is an auto box, check the fluid level first. After that check the fluid filter and pump. Then the brake bands. Then the torque converter. If a manual box it's either the layshaft bearings or synchro cones. A transmission shop will tell you for sure.
The reason your car is whining is because your car is low on tramission fluid. but i have checked my transmission fluid..? do i need to flush it out and get new transmission fluid?
A whining noise in the transmission is usually an indication the transmission fluid is low. Check the transmission fluid and fill it to the recommended level.
it has the wrong fluid in the transmission
Fan belt slipping
ON the 2006 impala that whining noise is actually the electronics when you accelerate. Its more or less electronic pulses/signals My 06 Impala is the same.
it can if it has uneven wear
It could be low on fluid, the syncros could be worn out. does it need fluid?
low fluid, internal bearing failure.
gears kicking, lots of whining noise??
Friction in the transmission system may cause whining noise when a car is accelerating. A poor engine or clutch assembly may cause the excess friction in the transmission system.
fluid braking down
My 2000 sebring did the same thing. I was told it was my temperamental transmission.