transmission problem

[costi]

Hello,
I own a 05 Altima SE-R since Jan 09 and didn't have any problems with the car. It has 68,000 miles and i service it at my local dealership. Since i bought it used i changed most of the fluids and the service tech recomanded me to change the oil in the transmission. I did that probabily 2 months ago. They didn't flush it , just drain and refill. After that, few days later i started having some problems with the transmission; for example i'm driving, the car is shifting normal and when i want to make a turn and I back off the gas, i step the brakes(i don't stop), the car slows down, i make the turn and i go back on gas then it shifts very hard, like something it's about to brake under me. This also happens when i go straight and i slow down and before i'm almost stopped i can feel that hard shifting again, but not as bad as in the case described above. I read a lot of posts and seems that a lot of people are experiencing problems when the car is upshifting(most from 1st to 2nd), in my case is when is downshifting, maybe i's wrong i don't know what the car is doing when i'm making a turn but i know it's not normal. And another thing that i'm not sure if it's related to the transmission issue that i have : when i back up the car from a parking position in the front makes a noise , sounds like a brake squeaking, a high pitched one. I do not have any mechanical knowledge and any input will be very appreciated. Thank you!

Costi