There certainly can a be a degree in difference of performance in 240D automatics. My parents owned 2 240D's at the same time. One was 79(123) and the other was a 76(115). The 76 model was MUCH more peppier(for a 240D) than the 79. The 79 for some reason was a bit slower. Especially fully loaded when going through the mountains of West Virginia. I remember it being so slow going up some mountains we thought it would roll backwards! The 76 got the job done much easier. Both were well maintained.
On a side note when my Dad purchased the 85 300SD in 1991(that I currently own) he was amazed at the performance difference. It replaced the 79 240D. Also not to jack the thread but I am very happy that I still have the car my Dad bought in 1991 with 76,000 miles. My parents got divorced in 94 and then my Mom drove it until she gave it to me in 2006. It is cool to drive/own the car you use to ride in the back seat in! On top of it being a wonderful car to this day.
I miss the 240D's we had when I was young. Would like to get a W115, or W123 one day. They have lots of character and are great cars.

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1985 Mercedes Benz 300SD, TMU
2015 Chrysler 200S