I had my tranny on my 81 sd back flushed an it shifts better.a definite no no on atf in the differential ,but you do use it in the manual tranny in the old 74 240 d sure surprised me when I first got the car and drained it for a refill ,as I had no manual at the time I called the dealer here in Eugene Or and they told me to use atf in the manual. By the way the people at the Eugene Or. M.B. dealership are the politest I have ever dealt with . The last time I called them the head tech man stopped what he was doing and came to the phone to answer my question.