1991 lumina Transmission problems??

[bobbarker123]

I have a 1991 lumina with the 3.1 4 speed with O/D Transmission it has bout 200,000 miles on it. No matter warm or cold there will be time when i drive ill be goin down a on ramp onto the interstate and my transmission wont shift out of second, ill be goin 75-80mph before i notice and i let off the gas and ofcourse it slows down very quickly and if you hit the gas it takes off pretty nice but you can here the engine RPMs and it sounds like it gonna blow. It does not do it all the time. there was a time when i left work it didnt do it i turned the car off and got gas and turned it back on and took off and it did it. I dont know it does it maybe 3 times a week if that. any help would be awesome but dont strain bout it cause im getting a 2007 monte carlo ss but i would like to keep this car for winter

[jeffcoslacker]

What do you have to do to get it to upshift when it does it?