I've got a 2003 S40 with 43000 mi. and recently the auto trans started acting up. When the car is 1st started and I back out of the drive it slams really hard when shifting from reverse to drive. I've checked the fluid level and it is at proper level both cold and hot(unless I'm checking it wrong.) It only does it after the initial start when the car is at high idle. The questions I have is this normal? and has anyone changed their own auto trans fluid and if so, whats involved and what fluid do you use? Thanks in advance for any input.