Hello guys I have some transmission shifting questions. I have a 1983 mercedes 300td wagon that I purchased. The car was sitting for 5 years. I got it running pretty well and fixed some small problems with it. I have a mity vac and have fixed a couple leaks. The door locks don't work for sure. I could push the master down and they would all go down. When I would pull it up they all wouldn't. Now the master is jammed. I tried to push it down with no luck I don't want to break it. I hooked my mighty vac to the main line and had 18.5 in of vacuum at idle. If I drive the car in d not in low it seems to shift to 3rd by 30mph. What would cause this? If I put it in low and shift manually it works well. Thanks for any help.