1984 190D 2.2L Automatic Transmission 114,000 miles. The transmission slips when it shifts. If you shift manually it works fine and after the car warms up it will then shift automatically. I searched and read some posts regarding transmissions and some posts talk about vacuum problems and by adjusting the modulator will fix. Could this be a vacuum problem or is the transmission bad and need to be rebuilt? Not sure why it would work fine after the car warms up if it was a vacuum problem.

Thanks in advance for your help,
Joe