I think my trans does this to.. I have a 4g64 2.4l and im not sure what trans it is yet besides a 4 speed automatic front wheel drive.(F4A23 ?) When i first start it up in the mornings it takes a lil bit more rpms then normal for it to move in reverse outta my parking spot then when it goes to shift into second it does what your describing, a slight slip catch slip then kicks back to normal. But after i get down the road its fine and will not do it all again all day unless it sits for hours. I noticed when im in park with it idling i think i can hear a fluid movement sound, kinda like a slurping sound coming from the trans area. Im bent on the idea its the pump. I thought maybe a seal but it only does it before the fluids had a chance to be circulated through the trans, then after that its fine. It has done this before and after a trans filter and fluid change. Problem has not got worse. Car shows 178k miles. I noticed also going down hill the down shift is a lil drastic, almost like being thrown into neutral. Would love to know why it does this.