The 240D used a 3.69/1 ratio the 1983 300SD had a 3.07/1. The engine will run much faster at 60MPH but would be much quicker from 0-60. Fuel consumption would increase as the engine would be revving too high except around town.

The diff would FIT! Possibly a input flange swap would be required.

__________________
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