There are a few adjustments on the SD that are not on other cars for the trans. There is the bowden cable the modulator valve and there is a valve on the rear of the injection pump that can fail and needs to be adjusted with a special tool. All three have to be right for all of the shifts to feel normal.
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM