Recently, I had my transmission fluid changed on my 06 GX 470 from my Lexus Dealer, I noticed that the transmission shifting is not smooth from 1st to 2nd , 2nd to 3rd and so i decided to check the transmission fluid level myself, to my surprised the transmission fluid came out right away when i loosened the 5mm allen check plug on the transmission. I drove my car to fully warmed up the transmission and the car is at idling when i did the procedure. Did my dealer overfilled my transmission and what is the correct way to check the fluid level.