@benzi, thanks for your query. We need to look at your vehicle first before i can advice you on the extent of the problem but to be brief, modern vehicles come with OBD(on board Diagnostics) systems. The car is fitted with an (ECU)Engine control unit which has the programs which control all the operations of your car and also gets reports from sensors place in the various parts of the car. If there is a problem in any system in the car, then this is reported to the ECUby the sensors.
what we do is we are able to scan the ECU and all the sensors to establish where the problem is. Once we establish the problem we directly deal with it without guess work.
Back to you problem, Your issue could be a malfunction in the ECU or some solenoids in the gearbox could be spoit.
Hope you are answered!