i have a 96 jimmy with a 4.3 v6 auto trans. over the past week, it has devloped a buck or jerk while shifting gears. it is a very noticable jerk and it causes the rpms to shoot up until it is in the next gear. i checked the fluid, it showed full, but i saw little bubbles in the fluid on the dipstick. i dont know what this means. can anyone give me some advice on why it s bucking? thanks