1984 300D Turbo Diesel Transmission Slipping?

[Melchoix]

Hello Diesel fans.... I have a 1984 300D Turbo Diesel that has I think a transmission that has been "slipping" lately. Dont know for sure if it's a transmission issue or not. Here are the symptoms: when the car is cold (below 80 deg C) the engine's rpm would shoot up past 3000rpm when I accelerate or go up a sloping road; then the car would go herky-jerky until I ease up on the gas pedal. Now, after the car has warmed up, it drives perfectly fine. The car has 235,000 miles on the clock. Any tips/fixes are appreciated.
Thank you in advance.