I own an '81 240D non-turbo that has 149k on her. When shes cold or pulling up a hill the trans seems like it lets the engine rev too high before it shifts and when it does the car slaps ahead almost like somebody tapped it from the back. Anyone who has a similar experience or ideas would be much appreciated.

 

Usually a lack of proper vacuum to the trans. Does this engine have a vacuum regulator assembly on top of the valve cover? if so, the white plastic vac valves there wear out and no longer regulate at the proper time. Also if the fluid in the trans hasn't been changed in the last 30,000 miles, do that with a new filter.