This Transmission is for the BONE STOCK Impala. not the LS or SS (sorry guys different transmission)
I got the transgo sk4t65e kit and changed accumulator springs and spacers, works great, really easy to do. drop pan, unbolt accumulator housing, pull out piston, replace spring with ones in kit and reinstall. takes about 160 bucks and about an hour of your time.
Step one buy the kit, go onto Ebay and search transgo sk4t65e kit. If you try to buy one of these at your trans/mechanic shops they will not have it or charge you a arm and a leg for it. On Ebay it cost Around or less than $60.
Go and Get some transmission fluid and a trans filter since you are going to removing all of the old fluid might as well do some preventative maintenance on your car as well as fixing a problem. I also put a drain plug in mine to make changing the fluid easy the next time