Vintage Cars: SL560, bowden cable, throttle linkage

Question
Hi Ron, forgot to mention that the SL hangs onto 1st gear for an extended time before it changes to 2nd, does this help with your diagnosis?
Michael

Answer
well my first thought would be the vacuum modulator.  Sometimes the line comes off or leaks.  It sits on the side of the tranny about midway, it can be adjusted . I think your car has a bowden cable like other 107's. It attatches to to throttle linkage at the back of the engine and runs down to the transmission. It "tells" the transmission what the throttle position is, so it will shift if you are giving it more gas.
There is a rod that connects the pivot with the cable to the throttle linkage. It should be adjusted so that the cable moves as soon as the throttle does.
Lastly may require a rebuild.  One thing you may try is to drain and replace filter in trans and see if that helps. Also by dropping the pan you can get an idea of any bits of metal are floating about
You probably need to get a manual of some sort to walk through these ideas
good luck