trany doesn't want to upshift

My 2001 G20 with 95k(actually my cousins) sometimes decides not to shift in the upper gears, lately it happens more and more often. Not sure if it stays in the first or the second but obviously does not go higher then that. In order for me to make it to shift I have to stop the car, shut it of, restart it and then it seems to shift fine. I changed the ATF and the filter that did have so metal shavings, but not nearly as much as I expected it to have with that kind of shifting. I also added some “snake oil” transmission magic hoping it would help some and it did for the first day & ½ but then it went right back to the old ways. Any ideas? I am lost & changing the trany is not an option :rolleyes:
Thanks!

My 2001 G20 with 95k(actually my cousins) sometimes decides not to shift in the upper gears, lately it happens more and more often. Not sure if it stays in the first or the second but obviously does not go higher then that. In order for me to make it to shift I have to stop the car, shut it of, restart it and then it seems to shift fine. I changed the ATF and the filter that did have so metal shavings, but not nearly as much as I expected it to have with that kind of shifting. I also added some “snake oil” transmission magic hoping it would help some and it did for the first day & ½ but then it went right back to the old ways. Any ideas? I am lost & changing the trany is not an option :rolleyes:
Thanks!

Hey There - I've got the same problem except that it doesn't matter if I turn the car on or off. Same issue - I also had the dealer tell me that they didn't find a problem after doing a diagnostic and road test. I've told them to go drive it again because I've been driving the car for over 1.5 years and it has never done this before. Can anyone help here?

- Jordan

YEah i am also having the same problem. HELP!!!