04 Impala transmission issue
 

My 04 Impala suddenly has transmission problem. I cannot switch to D and 3rd gear. When I do, it feel like similar to neutral. But 1,2 and reverse still work. I also hear fluid flowing sound when I press the gas pad, in d,3 and some times in 2.
Does any know what it is the cause? Do I have to have transmisiosn rebuild or something?

Thanks