I received a judgment about 9yrs ago,I cosigned for my sister to get a car after she missed payments they repoed it & put the judgment on both our credits! She paid on it 4 yrs ago & now I can do nothing,I'm trying to by a house, but this judgment is standing in my way,I was able to get transunion to take it off my credit, but the other wouldn't do it! I'm now trying to file a motion to vacate, but I don't know how... I need help, what should I do?

You co-signed the loan. That makes you responsible. No way you can get the judgment vacated