Kingstinger

Can anyone help me solve this problem? I have an 04 Rx8 automatic and recently it started making this whining noise coming from the transmission. It shifts into gear but as soon as i accelerate it makes that whining noise then after it heats up or warms up doesn't shift into gear (sounds like it just spins) It's out of warranty so the dealership would be my last option even though they are out of their mind telling me that they have never had a problem like this like every other problem i've have with this car.

Any suggestions? Please!!