The W126 chassis 300SD's use an electric central locking pump that has nothing in common with the engine vacuum systems...

The trans will still shift with the vacuum disconnected..just a harder shift.

__________________
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

did you change the trans fluid and filter[and drain torque converter]? david poole european performance dallas tx.

I believe that the '83 300SD uses the engine vacuum pump for this, and the '85 uses the electric pump. I do not know what's in the '84.