The W123 cars have a CABLE drives speedo. The W126 chassis has electronic speedo, therefore it uses an inductive pick-up. THE transmissions shouldn't be interchanged unless many parts are swapped. On the transmissions with inductive pick-up there isn't any lubrication nozzle at the speed drive gears.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator