1979 Mercedes Benz 300sd 6 cyl Two Wheel Drive Automatic 164000 miles
When accelerating the car does not shift properly into the next gear. It only shifts when you lift off the gas - but then if you hit the gas again it will shift down again. Car will not accelerate over a maximium of 40 miles per hour because it keeps shifting down.
The symptoms that you are experiencing sounds like a sift down table out of adjustment, we'll probably have a take it to a transmission shop, but if you want to try to do it I will assist you, I love enthusiasm! Just get back to me.