engine problems......i think

my car seems to take a long time to get in first gear.let me explain when i start my car and put in drive the engine seems to rev up at the normal rpms but the speed doesn't start till a little later.i have a friend that a retired auto mechanic that says it might be the vaccum modulator could he be right.i hope some1 here can help me already had some gaskets replaced but problem presist

Have you checked the fluid level, or if you have the "sealed" transmission on the newer grand ams, have you added some fluid? Sounds like low fluid to me.