My uncle had a prob like this in his Toyota Corolla wagon it got worse and he repaired the gear box from some place in negambo but after a few months the prob came again finally the car refused to move then we took it to Toyota Lanka and they said we have to replace the gear box and we did now its ok my advice for you is to take your vehicle somewhere you can really identify the prob like Toyota Lanka coz we really dont know whats going inside the gear box, just go to find out the problem after that you'll be able to find the solution Good luck....