I have a 1991 Subaru Legacy L with the standard 4-speed automatic transmission with lock up. Duty solenoid B within the transmission is responsible for the lock up however it's been failing or not working at all for a little while and when it does work it is weak. The transmission could probably use a good flush but I don't know if that would solve my problem at all Maybe the weak problem but I'm not sure if there is a short or something causing the transmission to not lock up or if Duty solenoid B is just dead.