Symbol 1166B from ISO 7000 - Title/Meaning: Transmission Function/description: To identify the general transmission symbol, to be used in conjunction with other symbols.
Additional information: 
On road vehicles: 

""+"" may be added to indicated up shift
""-"" may be added to indicated downshift.
Own work using: iso.org/obp/graphics/grs/86342e28-47ed-4524-bb53-9d0e75862671 200.png
Vectorization:  Mrmw