Toyota camry 1999

Question

Hello dear mechanics,

I am going to travel within the USA in the coming summer with my car, camry 1999 2.2 4 cylinder, InshAllah Buirsa, So I am preparing my car for the trip, I have already done these thing:

1)Put new tires
2)changed engine oil
3) changes transmission fluid

But, I have noticed that after having changed transmission fluid when I press the gas pedal I feel some kind of vibration with my foot, so what is the reason for that?

The second question is what else should i do with my car before starting my trip?

Thanks you for your answer in advance!