I have a 2000 cadillac seville with a 4t80e automatic transmission. My car stopped shifting into 5th gear at high speeds. It stays in 4th when maintaining my speed, or accelerating, and only shifts into 5th gear if i take my foot completely off the gas, or If i'm going downhill. I believe its the shift solenoids A&B, but I can't find any information saying if these are in charge of 5th gear, or if 5th gear is controlled by another solenoid that could be malfunctioning. Thank you