Usually my overdrive kicks in at around 50mph, but its not kicking in till i drive it for about a half an hour. It never used to do that. I had my trans. fluid changed and then it started. I have no idea what it is. I took it back and they said it was some valve sticking so they put lucas trans stuff in it and its gotten a little better, it will go into OD every once in a while now but its still not going all the time. Any suggestions?

Thanks

Jeff