Transmission Problems? Ask a Mechanic for Answers ASAP
Did you install a new throttle body or a used one?
Alright, it could have something to do with the transmission but it is strange that it started happening right after you replaced the throttle body. The transmission looks at the throttle position sensor to find shift points. It is possible that the throttle position sensor is the issue, or that the computer just needs to be reset. Try disconnecting the battery for an hour or so and then driving it again.