I have a 2001 DTS super clean and super low miles, tranny wont go into OD gear, new solenoids including TTC installed, new filters, no engine codes, the computer is sending a signal to shift onto OD only thing I would like to replace before throwing the flag is the 4th gear servo, RPM sits at about 3k around 65mph, I know where the servo is located, can I replace this without having to remove the tranny again?